jQuery handler not defined (handler.guid)

jQuery handler not defined (handler.guid) - javascript

i have a function for attaching handlers to events and it's working when a pass it an anonymous function but when i declare the function as a field in the object it doesn't work and the handler is undefined
validationObj = (function(API){
this.validate = function (id2, idN2){
//code
//doesn't work
//this way i get an handler.guid error on functionFromMyApi
API.attach_events( {"keyup": run_func(id1, id2) },"id");
// work's ok
API.attach_events( {"keyup": function(){
// same code here from run_func
}
},"id");
//code
};
var run_func = function (id1, id2){
var obj1 = document.getElementById(id1);
var obj2= document.getElementById(id2);
var show_err = false;
API.functionFromMyApi ();
//code
// more code
};
})(api);
i use jQuery 1.2.6

When you do:
API.attach_events( {"keyup": run_func(id1, id2) },"id");
you're not passing it a function reference, like you do when you use an anonymous function, you're instead calling run_func and passing its return value. If run_func had no parameters then you could do:
API.attach_events( {"keyup": run_func},"id");
However, since it does, you're still going to need to use an anonymous function:
API.attach_events( {"keyup": function() {run_func(id1, id2)} },"id");

Related

Probably a really simple thing but I can't seem to pass an argument into my Javascript function [duplicate]

The situation is somewhat like-
var someVar = some_other_function();
someObj.addEventListener("click", function(){
some_function(someVar);
}, false);
The problem is that the value of someVar is not visible inside the listener function of the addEventListener, where it is probably being treated as a new variable.

Why not just get the arguments from the target attribute of the event?
Example:
const someInput = document.querySelector('button');
someInput.addEventListener('click', myFunc, false);
someInput.myParam = 'This is my parameter';
function myFunc(evt)
{
window.alert(evt.currentTarget.myParam);
}
<button class="input">Show parameter</button>
JavaScript is a prototype-oriented language, remember!

There is absolutely nothing wrong with the code you've written. Both some_function and someVar should be accessible, in case they were available in the context where anonymous
function() { some_function(someVar); }
was created.
Check if the alert gives you the value you've been looking for, be sure it will be accessible in the scope of anonymous function (unless you have more code that operates on the same someVar variable next to the call to addEventListener)
var someVar;
someVar = some_other_function();
alert(someVar);
someObj.addEventListener("click", function(){
some_function(someVar);
}, false);

This question is old but I thought I'd offer an alternative using ES5's .bind() - for posterity. :)
function some_func(otherFunc, ev) {
// magic happens
}
someObj.addEventListener("click", some_func.bind(null, some_other_func), false);
Just be aware that you need to set up your listener function with the first param as the argument you're passing into bind (your other function) and the second param is now the event (instead of the first, as it would have been).

Quite and old question but I had the same issue today. Cleanest solution I found is to use the concept of currying.
The code for that:
someObj.addEventListener('click', some_function(someVar));
var some_function = function(someVar) {
return function curried_func(e) {
// do something here
}
}
By naming the curried function it allows you to call Object.removeEventListener to unregister the eventListener at a later execution time.

You can just bind all necessary arguments with 'bind':
root.addEventListener('click', myPrettyHandler.bind(null, event, arg1, ... ));
In this way you'll always get the event, arg1, and other stuff passed to myPrettyHandler.
http://passy.svbtle.com/partial-application-in-javascript-using-bind

nice one line alternative
element.addEventListener('dragstart',(evt) => onDragStart(param1, param2, param3, evt));
function onDragStart(param1, param2, param3, evt) {
//some action...
}

You can add and remove eventlisteners with arguments by declaring a function as a variable.
myaudio.addEventListener('ended',funcName=function(){newSrc(myaudio)},false);
newSrc is the method with myaudio as parameter
funcName is the function name variable
You can remove the listener with
myaudio.removeEventListener('ended',func,false);

Function.prototype.bind() is the way to bind a target function to a particular scope and optionally define the this object within the target function.
someObj.addEventListener("click", some_function.bind(this), false);
Or to capture some of the lexical scope, for example in a loop:
someObj.addEventListener("click", some_function.bind(this, arg1, arg2), false);
Finally, if the this parameter is not needed within the target function:
someObj.addEventListener("click", some_function.bind(null, arg1, arg2), false);

You could pass somevar by value(not by reference) via a javascript feature known as closure:
var someVar='origin';
func = function(v){
console.log(v);
}
document.addEventListener('click',function(someVar){
return function(){func(someVar)}
}(someVar));
someVar='changed'
Or you could write a common wrap function such as wrapEventCallback:
function wrapEventCallback(callback){
var args = Array.prototype.slice.call(arguments, 1);
return function(e){
callback.apply(this, args)
}
}
var someVar='origin';
func = function(v){
console.log(v);
}
document.addEventListener('click',wrapEventCallback(func,someVar))
someVar='changed'
Here wrapEventCallback(func,var1,var2) is like:
func.bind(null, var1,var2)

Here's yet another way (This one works inside for loops):
var someVar = some_other_function();
someObj.addEventListener("click",
function(theVar){
return function(){some_function(theVar)};
}(someVar),
false);

someVar value should be accessible only in some_function() context, not from listener's.
If you like to have it within listener, you must do something like:
someObj.addEventListener("click",
function(){
var newVar = someVar;
some_function(someVar);
},
false);
and use newVar instead.
The other way is to return someVar value from some_function() for using it further in listener (as a new local var):
var someVar = some_function(someVar);

one easy way to execute that may be this
window.addEventListener('click', (e) => functionHandler(e, ...args));
Works for me.

Use
el.addEventListener('click',
function(){
// this will give you the id value
alert(this.id);
},
false);
And if you want to pass any custom value into this anonymous function then the easiest way to do it is
// this will dynamically create property a property
// you can create anything like el.<your variable>
el.myvalue = "hello world";
el.addEventListener('click',
function(){
//this will show you the myvalue
alert(el.myvalue);
// this will give you the id value
alert(this.id);
},
false);
Works perfectly in my project. Hope this will help

If I'm not mistaken using calling the function with bind actually creates a new function that is returned by the bind method. This will cause you problems later or if you would like to remove the event listener, as it's basically like an anonymous function:
// Possible:
function myCallback() { /* code here */ }
someObject.addEventListener('event', myCallback);
someObject.removeEventListener('event', myCallback);
// Not Possible:
function myCallback() { /* code here */ }
someObject.addEventListener('event', function() { myCallback });
someObject.removeEventListener('event', /* can't remove anonymous function */);
So take that in mind.
If you are using ES6 you could do the same as suggested but a bit cleaner:
someObject.addEventListener('event', () => myCallback(params));

$form.addEventListener('submit', save.bind(null, data, keyword, $name.value, myStemComment));
function save(data, keyword, name, comment, event) {
This is how I got event passed properly.

One way is doing this with an outer function:
elem.addEventListener('click', (function(numCopy) {
return function() {
alert(numCopy)
};
})(num));
This method of wrapping an anonymous function in parentheses and calling it right away is called an IIFE (Immediately-Invoked Function Expression)
You can check an example with two parameters in http://codepen.io/froucher/pen/BoWwgz.
catimg.addEventListener('click', (function(c, i){
return function() {
c.meows++;
i.textContent = c.name + '\'s meows are: ' + c.meows;
}
})(cat, catmeows));

In 2019, lots of api changes, the best answer no longer works, without fix bug.
share some working code.
Inspired by all above answer.
button_element = document.getElementById('your-button')
button_element.setAttribute('your-parameter-name',your-parameter-value);
button_element.addEventListener('click', your_function);
function your_function(event)
{
//when click print the parameter value
console.log(event.currentTarget.attributes.your-parameter-name.value;)
}

Sending arguments to an eventListener's callback function requires creating an isolated function and passing arguments to that isolated function.
Here's a nice little helper function you can use. Based on "hello world's" example above.)
One thing that is also needed is to maintain a reference to the function so we can remove the listener cleanly.
// Lambda closure chaos.
//
// Send an anonymous function to the listener, but execute it immediately.
// This will cause the arguments are captured, which is useful when running
// within loops.
//
// The anonymous function returns a closure, that will be executed when
// the event triggers. And since the arguments were captured, any vars
// that were sent in will be unique to the function.
function addListenerWithArgs(elem, evt, func, vars){
var f = function(ff, vv){
return (function (){
ff(vv);
});
}(func, vars);
elem.addEventListener(evt, f);
return f;
}
// Usage:
function doSomething(withThis){
console.log("withThis", withThis);
}
// Capture the function so we can remove it later.
var storeFunc = addListenerWithArgs(someElem, "click", doSomething, "foo");
// To remove the listener, use the normal routine:
someElem.removeEventListener("click", storeFunc);

There is a special variable inside all functions: arguments. You can pass your parameters as anonymous parameters and access them (by order) through the arguments variable.
Example:
var someVar = some_other_function();
someObj.addEventListener("click", function(someVar){
some_function(arguments[0]);
}, false);

I was stuck in this as I was using it in a loop for finding elements and adding listner to it. If you're using it in a loop, then this will work perfectly
for (var i = 0; i < states_array.length; i++) {
var link = document.getElementById('apply_'+states_array[i].state_id);
link.my_id = i;
link.addEventListener('click', function(e) {
alert(e.target.my_id);
some_function(states_array[e.target.my_id].css_url);
});
}

I suggest you to do something like that:
var someVar = some_other_function();
someObj.addEventListener("click", (event, param1 = someVar) => {
some_function(param1);
}, false);

The PERFECT SOLUTION for this is to use Closures like this:
function makeSizer(size) {
return function () {
document.body.style.fontSize = `${size}px`;
};
}
//pass parameters here and keep the reference in variables:
const size12 = makeSizer(12);
const size24 = makeSizer(24);
const size36 = makeSizer(36);
document.getElementById('size-12').addEventListener("click", size12);
document.getElementById('size-24').addEventListener("click", size24);
document.getElementById('size-36').addEventListener("click", size36);
document.getElementById('remove-12').addEventListener("click", ()=>{
document.getElementById('size-12').removeEventListener("click", size12);
alert("Now click on 'size 12' button and you will see that there is no event listener any more");
});
test<br/>
<button id="size-12">
size 12
</button>
<button id="size-24">
size 24
</button>
<button id="size-36">
size 36
</button>
<button id="remove-12">
remove 12
</button>
So basically you wrap a function inside another function and assign that to a variable that you can register as an event listener, but also unregister as well!

Also try these (IE8 + Chrome. I dont know for FF):
function addEvent(obj, type, fn) {
eval('obj.on'+type+'=fn');
}
function removeEvent(obj, type) {
eval('obj.on'+type+'=null');
}
// Use :
function someFunction (someArg) {alert(someArg);}
var object=document.getElementById('somObject_id') ;
var someArg="Hi there !";
var func=function(){someFunction (someArg)};
// mouseover is inactive
addEvent (object, 'mouseover', func);
// mouseover is now active
addEvent (object, 'mouseover');
// mouseover is inactive
Hope there is no typos :-)

The following answer is correct but the below code is not working in IE8 if suppose you compressed the js file using yuicompressor. (In fact,still most of the US peoples using IE8)
var someVar;
someVar = some_other_function();
alert(someVar);
someObj.addEventListener("click",
function(){
some_function(someVar);
},
false);
So, we can fix the above issue as follows and it works fine in all browsers
var someVar, eventListnerFunc;
someVar = some_other_function();
eventListnerFunc = some_function(someVar);
someObj.addEventListener("click", eventListnerFunc, false);
Hope, it would be useful for some one who is compressing the js file in production environment.
Good Luck!!

var EV = {
ev: '',
fn: '',
elem: '',
add: function () {
this.elem.addEventListener(this.ev, this.fn, false);
}
};
function cons() {
console.log('some what');
}
EV.ev = 'click';
EV.fn = cons;
EV.elem = document.getElementById('body');
EV.add();
//If you want to add one more listener for load event then simply add this two lines of code:
EV.ev = 'load';
EV.add();

The following approach worked well for me. Modified from here.
function callback(theVar) {
return function() {
theVar();
}
}
function some_other_function() {
document.body.innerHTML += "made it.";
}
var someVar = some_other_function;
document.getElementById('button').addEventListener('click', callback(someVar));
<!DOCTYPE html>
<html>
<body>
<button type="button" id="button">Click Me!</button>
</body>
</html>

Since your event listener is 'click', you can:
someObj.setAttribute("onclick", "function(parameter)");

Another workaround is by Using data attributes
function func(){
console.log(this.dataset.someVar);
div.removeEventListener("click", func);
}
var div = document.getElementById("some-div");
div.setAttribute("data-some-var", "hello");
div.addEventListener("click", func);
jsfiddle

The following code worked fine for me (firefox):
for (var i=0; i<3; i++) {
element = new ... // create your element
element.counter = i;
element.addEventListener('click', function(e){
console.log(this.counter);
... // another code with this element
}, false);
}
Output:
0
1
2

You need:
newElem.addEventListener('click', {
handleEvent: function (event) {
clickImg(parameter);
}
});

Attaching different eventListeners for each item in for-of-loop [duplicate]

The situation is somewhat like-
var someVar = some_other_function();
someObj.addEventListener("click", function(){
some_function(someVar);
}, false);
The problem is that the value of someVar is not visible inside the listener function of the addEventListener, where it is probably being treated as a new variable.

Why not just get the arguments from the target attribute of the event?
Example:
const someInput = document.querySelector('button');
someInput.addEventListener('click', myFunc, false);
someInput.myParam = 'This is my parameter';
function myFunc(evt)
{
window.alert(evt.currentTarget.myParam);
}
<button class="input">Show parameter</button>
JavaScript is a prototype-oriented language, remember!

There is absolutely nothing wrong with the code you've written. Both some_function and someVar should be accessible, in case they were available in the context where anonymous
function() { some_function(someVar); }
was created.
Check if the alert gives you the value you've been looking for, be sure it will be accessible in the scope of anonymous function (unless you have more code that operates on the same someVar variable next to the call to addEventListener)
var someVar;
someVar = some_other_function();
alert(someVar);
someObj.addEventListener("click", function(){
some_function(someVar);
}, false);

This question is old but I thought I'd offer an alternative using ES5's .bind() - for posterity. :)
function some_func(otherFunc, ev) {
// magic happens
}
someObj.addEventListener("click", some_func.bind(null, some_other_func), false);
Just be aware that you need to set up your listener function with the first param as the argument you're passing into bind (your other function) and the second param is now the event (instead of the first, as it would have been).

Quite and old question but I had the same issue today. Cleanest solution I found is to use the concept of currying.
The code for that:
someObj.addEventListener('click', some_function(someVar));
var some_function = function(someVar) {
return function curried_func(e) {
// do something here
}
}
By naming the curried function it allows you to call Object.removeEventListener to unregister the eventListener at a later execution time.

You can just bind all necessary arguments with 'bind':
root.addEventListener('click', myPrettyHandler.bind(null, event, arg1, ... ));
In this way you'll always get the event, arg1, and other stuff passed to myPrettyHandler.
http://passy.svbtle.com/partial-application-in-javascript-using-bind

nice one line alternative
element.addEventListener('dragstart',(evt) => onDragStart(param1, param2, param3, evt));
function onDragStart(param1, param2, param3, evt) {
//some action...
}

You can add and remove eventlisteners with arguments by declaring a function as a variable.
myaudio.addEventListener('ended',funcName=function(){newSrc(myaudio)},false);
newSrc is the method with myaudio as parameter
funcName is the function name variable
You can remove the listener with
myaudio.removeEventListener('ended',func,false);

Function.prototype.bind() is the way to bind a target function to a particular scope and optionally define the this object within the target function.
someObj.addEventListener("click", some_function.bind(this), false);
Or to capture some of the lexical scope, for example in a loop:
someObj.addEventListener("click", some_function.bind(this, arg1, arg2), false);
Finally, if the this parameter is not needed within the target function:
someObj.addEventListener("click", some_function.bind(null, arg1, arg2), false);

You could pass somevar by value(not by reference) via a javascript feature known as closure:
var someVar='origin';
func = function(v){
console.log(v);
}
document.addEventListener('click',function(someVar){
return function(){func(someVar)}
}(someVar));
someVar='changed'
Or you could write a common wrap function such as wrapEventCallback:
function wrapEventCallback(callback){
var args = Array.prototype.slice.call(arguments, 1);
return function(e){
callback.apply(this, args)
}
}
var someVar='origin';
func = function(v){
console.log(v);
}
document.addEventListener('click',wrapEventCallback(func,someVar))
someVar='changed'
Here wrapEventCallback(func,var1,var2) is like:
func.bind(null, var1,var2)

Here's yet another way (This one works inside for loops):
var someVar = some_other_function();
someObj.addEventListener("click",
function(theVar){
return function(){some_function(theVar)};
}(someVar),
false);

someVar value should be accessible only in some_function() context, not from listener's.
If you like to have it within listener, you must do something like:
someObj.addEventListener("click",
function(){
var newVar = someVar;
some_function(someVar);
},
false);
and use newVar instead.
The other way is to return someVar value from some_function() for using it further in listener (as a new local var):
var someVar = some_function(someVar);

one easy way to execute that may be this
window.addEventListener('click', (e) => functionHandler(e, ...args));
Works for me.

Use
el.addEventListener('click',
function(){
// this will give you the id value
alert(this.id);
},
false);
And if you want to pass any custom value into this anonymous function then the easiest way to do it is
// this will dynamically create property a property
// you can create anything like el.<your variable>
el.myvalue = "hello world";
el.addEventListener('click',
function(){
//this will show you the myvalue
alert(el.myvalue);
// this will give you the id value
alert(this.id);
},
false);
Works perfectly in my project. Hope this will help

If I'm not mistaken using calling the function with bind actually creates a new function that is returned by the bind method. This will cause you problems later or if you would like to remove the event listener, as it's basically like an anonymous function:
// Possible:
function myCallback() { /* code here */ }
someObject.addEventListener('event', myCallback);
someObject.removeEventListener('event', myCallback);
// Not Possible:
function myCallback() { /* code here */ }
someObject.addEventListener('event', function() { myCallback });
someObject.removeEventListener('event', /* can't remove anonymous function */);
So take that in mind.
If you are using ES6 you could do the same as suggested but a bit cleaner:
someObject.addEventListener('event', () => myCallback(params));

$form.addEventListener('submit', save.bind(null, data, keyword, $name.value, myStemComment));
function save(data, keyword, name, comment, event) {
This is how I got event passed properly.

One way is doing this with an outer function:
elem.addEventListener('click', (function(numCopy) {
return function() {
alert(numCopy)
};
})(num));
This method of wrapping an anonymous function in parentheses and calling it right away is called an IIFE (Immediately-Invoked Function Expression)
You can check an example with two parameters in http://codepen.io/froucher/pen/BoWwgz.
catimg.addEventListener('click', (function(c, i){
return function() {
c.meows++;
i.textContent = c.name + '\'s meows are: ' + c.meows;
}
})(cat, catmeows));

In 2019, lots of api changes, the best answer no longer works, without fix bug.
share some working code.
Inspired by all above answer.
button_element = document.getElementById('your-button')
button_element.setAttribute('your-parameter-name',your-parameter-value);
button_element.addEventListener('click', your_function);
function your_function(event)
{
//when click print the parameter value
console.log(event.currentTarget.attributes.your-parameter-name.value;)
}

Sending arguments to an eventListener's callback function requires creating an isolated function and passing arguments to that isolated function.
Here's a nice little helper function you can use. Based on "hello world's" example above.)
One thing that is also needed is to maintain a reference to the function so we can remove the listener cleanly.
// Lambda closure chaos.
//
// Send an anonymous function to the listener, but execute it immediately.
// This will cause the arguments are captured, which is useful when running
// within loops.
//
// The anonymous function returns a closure, that will be executed when
// the event triggers. And since the arguments were captured, any vars
// that were sent in will be unique to the function.
function addListenerWithArgs(elem, evt, func, vars){
var f = function(ff, vv){
return (function (){
ff(vv);
});
}(func, vars);
elem.addEventListener(evt, f);
return f;
}
// Usage:
function doSomething(withThis){
console.log("withThis", withThis);
}
// Capture the function so we can remove it later.
var storeFunc = addListenerWithArgs(someElem, "click", doSomething, "foo");
// To remove the listener, use the normal routine:
someElem.removeEventListener("click", storeFunc);

There is a special variable inside all functions: arguments. You can pass your parameters as anonymous parameters and access them (by order) through the arguments variable.
Example:
var someVar = some_other_function();
someObj.addEventListener("click", function(someVar){
some_function(arguments[0]);
}, false);

I was stuck in this as I was using it in a loop for finding elements and adding listner to it. If you're using it in a loop, then this will work perfectly
for (var i = 0; i < states_array.length; i++) {
var link = document.getElementById('apply_'+states_array[i].state_id);
link.my_id = i;
link.addEventListener('click', function(e) {
alert(e.target.my_id);
some_function(states_array[e.target.my_id].css_url);
});
}

I suggest you to do something like that:
var someVar = some_other_function();
someObj.addEventListener("click", (event, param1 = someVar) => {
some_function(param1);
}, false);

The PERFECT SOLUTION for this is to use Closures like this:
function makeSizer(size) {
return function () {
document.body.style.fontSize = `${size}px`;
};
}
//pass parameters here and keep the reference in variables:
const size12 = makeSizer(12);
const size24 = makeSizer(24);
const size36 = makeSizer(36);
document.getElementById('size-12').addEventListener("click", size12);
document.getElementById('size-24').addEventListener("click", size24);
document.getElementById('size-36').addEventListener("click", size36);
document.getElementById('remove-12').addEventListener("click", ()=>{
document.getElementById('size-12').removeEventListener("click", size12);
alert("Now click on 'size 12' button and you will see that there is no event listener any more");
});
test<br/>
<button id="size-12">
size 12
</button>
<button id="size-24">
size 24
</button>
<button id="size-36">
size 36
</button>
<button id="remove-12">
remove 12
</button>
So basically you wrap a function inside another function and assign that to a variable that you can register as an event listener, but also unregister as well!

Also try these (IE8 + Chrome. I dont know for FF):
function addEvent(obj, type, fn) {
eval('obj.on'+type+'=fn');
}
function removeEvent(obj, type) {
eval('obj.on'+type+'=null');
}
// Use :
function someFunction (someArg) {alert(someArg);}
var object=document.getElementById('somObject_id') ;
var someArg="Hi there !";
var func=function(){someFunction (someArg)};
// mouseover is inactive
addEvent (object, 'mouseover', func);
// mouseover is now active
addEvent (object, 'mouseover');
// mouseover is inactive
Hope there is no typos :-)

The following answer is correct but the below code is not working in IE8 if suppose you compressed the js file using yuicompressor. (In fact,still most of the US peoples using IE8)
var someVar;
someVar = some_other_function();
alert(someVar);
someObj.addEventListener("click",
function(){
some_function(someVar);
},
false);
So, we can fix the above issue as follows and it works fine in all browsers
var someVar, eventListnerFunc;
someVar = some_other_function();
eventListnerFunc = some_function(someVar);
someObj.addEventListener("click", eventListnerFunc, false);
Hope, it would be useful for some one who is compressing the js file in production environment.
Good Luck!!

var EV = {
ev: '',
fn: '',
elem: '',
add: function () {
this.elem.addEventListener(this.ev, this.fn, false);
}
};
function cons() {
console.log('some what');
}
EV.ev = 'click';
EV.fn = cons;
EV.elem = document.getElementById('body');
EV.add();
//If you want to add one more listener for load event then simply add this two lines of code:
EV.ev = 'load';
EV.add();

The following approach worked well for me. Modified from here.
function callback(theVar) {
return function() {
theVar();
}
}
function some_other_function() {
document.body.innerHTML += "made it.";
}
var someVar = some_other_function;
document.getElementById('button').addEventListener('click', callback(someVar));
<!DOCTYPE html>
<html>
<body>
<button type="button" id="button">Click Me!</button>
</body>
</html>

Since your event listener is 'click', you can:
someObj.setAttribute("onclick", "function(parameter)");

Another workaround is by Using data attributes
function func(){
console.log(this.dataset.someVar);
div.removeEventListener("click", func);
}
var div = document.getElementById("some-div");
div.setAttribute("data-some-var", "hello");
div.addEventListener("click", func);
jsfiddle

The following code worked fine for me (firefox):
for (var i=0; i<3; i++) {
element = new ... // create your element
element.counter = i;
element.addEventListener('click', function(e){
console.log(this.counter);
... // another code with this element
}, false);
}
Output:
0
1
2

You need:
newElem.addEventListener('click', {
handleEvent: function (event) {
clickImg(parameter);
}
});

probably moronic js syntax error. Object is null

var fbToggle = document.getElementById("fbToggle");
and later in the script
fbToggle.addEventListener("click", toggle("fbContainer"));
Console tells me that fbToggle is NULL
This is in the document though.
<input type="checkbox" id="fbToggle">
I wasnt using eventListener before, so maybe there is a special order of declaration i'm missing ?
EDIT :
entire js :
function toggle(target) {
var obj = document.getElementById(target);
display = obj.style.display;
if (display == "none") {display = "block"}
else {display = "none"}
}
function init() {
var fbToggle = document.getElementById("fbToggle");
var twitToggle = document.getElementById("twitToggle");
var pinToggle = document.getElementById("pinToggle");
console.log(fbToggle); // NULL
fbToggle.addEventListener("click", toggle("fbContainer"));
twitToggle.addEventListener("click", toggle("twitContainer"));
pinToggle.addEventListener("click", toggle("pinContainer"));
}
window.onload = init();
HTML is way too long.but JS is in head, called from external file. Also i'm not in quirk mode.

It is not clear where "later in the script" is. If it is in different scope definitely it is not going to work. Suggesting you to keep everything in a global object if possible so that you can access from different places in the script.
window.globals = {};
window.globals.fbToggle = document.getElementById("fbToggle");
window.globals.fbToggle.addEventListener("click", function () {
toggle("fbContainer")
});
function toggle(container) {
alert(container);
}
http://jsfiddle.net/ST938/
Another point is addEventListener expects a function or function idenitifier, NOT a function call.
addEventListener("click", toggle("fbContainer")); // wrong
addEventListener("click", toggle); // correct
So if you want to pass a parameter
window.globals.fbToggle.addEventListener("click", function () {
toggle("fbContainer")
});
function toggle(container) {
alert(container);
}

In JavaScript, putting brackets after a function name causes it to be called. If you want to reference a function without calling it you must not put brackets after the name:
window.onload = init(); // this calls init() immediately
window.onload = init; // this correctly stores init in window.onload
The same applies to toggle(). If you need to pre-specify some of the arguments you can wrap it in an anonymous function:
fbToggle.addEventListener("click", function() { toggle("fbContainer"); });
or you can use bind:
fbToggle.addEventListener("click", toggle.bind(null, "fbContainer"));

jQuery binding function on focus

I'm writing a little plugin for jQuery and so far I've got this:
(function($){
$.fn.extend({
someFunction: function() {
return this.each(function() {
var obj = $(this);
obj.focus(someInternalFunction(obj));
});
}
});
function someInternalFunction(obj) {
};
})(jQuery);
The problem is, when i attach someFunction to the object, the object gets focus and binding of someInternalFunction on focus event fails.
Then I tried to bind function to wrap the function call in the other function:
obj.focus(function() {
someInternalFunction($(this));
});
This code works, but it isn't pretty at all. Is it possible to bind function on focus without wrapping it in the other function?

$.fn.bindFocus() = function(){
var internalFunction = function(){
var $this = $(this),
self = this;
// try do stuff here
};
return this.each(function(){
$(this).bind('focus', internalFunction);
});
}
$('#myElement').bindFocus();
Hope it'll help ?
EDT. Sorry, first time get you wrong :)

Here:
obj.focus(someInternalFunction(obj));
^^^^^
... you're calling the function, meaning that its return value is the thing that actually ends up being passed to focus(). Instead you want to pass a function to focus(). Given the fact that you want to pass obj to someInternalFunction, you'll have to define an additional function to wrap it all:
obj.focus(function(){
someInternalFunction(obj);
});
Just to make things clear:
var x = function() { return 3; }; // Defining a function
x; // -> this is a function reference
x(); // -> this is 3

How to pass arguments to addEventListener listener function?

The situation is somewhat like-
var someVar = some_other_function();
someObj.addEventListener("click", function(){
some_function(someVar);
}, false);
The problem is that the value of someVar is not visible inside the listener function of the addEventListener, where it is probably being treated as a new variable.

Why not just get the arguments from the target attribute of the event?
Example:
const someInput = document.querySelector('button');
someInput.addEventListener('click', myFunc, false);
someInput.myParam = 'This is my parameter';
function myFunc(evt)
{
window.alert(evt.currentTarget.myParam);
}
<button class="input">Show parameter</button>
JavaScript is a prototype-oriented language, remember!

There is absolutely nothing wrong with the code you've written. Both some_function and someVar should be accessible, in case they were available in the context where anonymous
function() { some_function(someVar); }
was created.
Check if the alert gives you the value you've been looking for, be sure it will be accessible in the scope of anonymous function (unless you have more code that operates on the same someVar variable next to the call to addEventListener)
var someVar;
someVar = some_other_function();
alert(someVar);
someObj.addEventListener("click", function(){
some_function(someVar);
}, false);

This question is old but I thought I'd offer an alternative using ES5's .bind() - for posterity. :)
function some_func(otherFunc, ev) {
// magic happens
}
someObj.addEventListener("click", some_func.bind(null, some_other_func), false);
Just be aware that you need to set up your listener function with the first param as the argument you're passing into bind (your other function) and the second param is now the event (instead of the first, as it would have been).

Quite and old question but I had the same issue today. Cleanest solution I found is to use the concept of currying.
The code for that:
someObj.addEventListener('click', some_function(someVar));
var some_function = function(someVar) {
return function curried_func(e) {
// do something here
}
}
By naming the curried function it allows you to call Object.removeEventListener to unregister the eventListener at a later execution time.

You can just bind all necessary arguments with 'bind':
root.addEventListener('click', myPrettyHandler.bind(null, event, arg1, ... ));
In this way you'll always get the event, arg1, and other stuff passed to myPrettyHandler.
http://passy.svbtle.com/partial-application-in-javascript-using-bind

nice one line alternative
element.addEventListener('dragstart',(evt) => onDragStart(param1, param2, param3, evt));
function onDragStart(param1, param2, param3, evt) {
//some action...
}

You can add and remove eventlisteners with arguments by declaring a function as a variable.
myaudio.addEventListener('ended',funcName=function(){newSrc(myaudio)},false);
newSrc is the method with myaudio as parameter
funcName is the function name variable
You can remove the listener with
myaudio.removeEventListener('ended',func,false);

Function.prototype.bind() is the way to bind a target function to a particular scope and optionally define the this object within the target function.
someObj.addEventListener("click", some_function.bind(this), false);
Or to capture some of the lexical scope, for example in a loop:
someObj.addEventListener("click", some_function.bind(this, arg1, arg2), false);
Finally, if the this parameter is not needed within the target function:
someObj.addEventListener("click", some_function.bind(null, arg1, arg2), false);

You could pass somevar by value(not by reference) via a javascript feature known as closure:
var someVar='origin';
func = function(v){
console.log(v);
}
document.addEventListener('click',function(someVar){
return function(){func(someVar)}
}(someVar));
someVar='changed'
Or you could write a common wrap function such as wrapEventCallback:
function wrapEventCallback(callback){
var args = Array.prototype.slice.call(arguments, 1);
return function(e){
callback.apply(this, args)
}
}
var someVar='origin';
func = function(v){
console.log(v);
}
document.addEventListener('click',wrapEventCallback(func,someVar))
someVar='changed'
Here wrapEventCallback(func,var1,var2) is like:
func.bind(null, var1,var2)

Here's yet another way (This one works inside for loops):
var someVar = some_other_function();
someObj.addEventListener("click",
function(theVar){
return function(){some_function(theVar)};
}(someVar),
false);

someVar value should be accessible only in some_function() context, not from listener's.
If you like to have it within listener, you must do something like:
someObj.addEventListener("click",
function(){
var newVar = someVar;
some_function(someVar);
},
false);
and use newVar instead.
The other way is to return someVar value from some_function() for using it further in listener (as a new local var):
var someVar = some_function(someVar);

one easy way to execute that may be this
window.addEventListener('click', (e) => functionHandler(e, ...args));
Works for me.

$form.addEventListener('submit', save.bind(null, data, keyword, $name.value, myStemComment));
function save(data, keyword, name, comment, event) {
This is how I got event passed properly.

Use
el.addEventListener('click',
function(){
// this will give you the id value
alert(this.id);
},
false);
And if you want to pass any custom value into this anonymous function then the easiest way to do it is
// this will dynamically create property a property
// you can create anything like el.<your variable>
el.myvalue = "hello world";
el.addEventListener('click',
function(){
//this will show you the myvalue
alert(el.myvalue);
// this will give you the id value
alert(this.id);
},
false);
Works perfectly in my project. Hope this will help

If I'm not mistaken using calling the function with bind actually creates a new function that is returned by the bind method. This will cause you problems later or if you would like to remove the event listener, as it's basically like an anonymous function:
// Possible:
function myCallback() { /* code here */ }
someObject.addEventListener('event', myCallback);
someObject.removeEventListener('event', myCallback);
// Not Possible:
function myCallback() { /* code here */ }
someObject.addEventListener('event', function() { myCallback });
someObject.removeEventListener('event', /* can't remove anonymous function */);
So take that in mind.
If you are using ES6 you could do the same as suggested but a bit cleaner:
someObject.addEventListener('event', () => myCallback(params));

One way is doing this with an outer function:
elem.addEventListener('click', (function(numCopy) {
return function() {
alert(numCopy)
};
})(num));
This method of wrapping an anonymous function in parentheses and calling it right away is called an IIFE (Immediately-Invoked Function Expression)
You can check an example with two parameters in http://codepen.io/froucher/pen/BoWwgz.
catimg.addEventListener('click', (function(c, i){
return function() {
c.meows++;
i.textContent = c.name + '\'s meows are: ' + c.meows;
}
})(cat, catmeows));

In 2019, lots of api changes, the best answer no longer works, without fix bug.
share some working code.
Inspired by all above answer.
button_element = document.getElementById('your-button')
button_element.setAttribute('your-parameter-name',your-parameter-value);
button_element.addEventListener('click', your_function);
function your_function(event)
{
//when click print the parameter value
console.log(event.currentTarget.attributes.your-parameter-name.value;)
}

Sending arguments to an eventListener's callback function requires creating an isolated function and passing arguments to that isolated function.
Here's a nice little helper function you can use. Based on "hello world's" example above.)
One thing that is also needed is to maintain a reference to the function so we can remove the listener cleanly.
// Lambda closure chaos.
//
// Send an anonymous function to the listener, but execute it immediately.
// This will cause the arguments are captured, which is useful when running
// within loops.
//
// The anonymous function returns a closure, that will be executed when
// the event triggers. And since the arguments were captured, any vars
// that were sent in will be unique to the function.
function addListenerWithArgs(elem, evt, func, vars){
var f = function(ff, vv){
return (function (){
ff(vv);
});
}(func, vars);
elem.addEventListener(evt, f);
return f;
}
// Usage:
function doSomething(withThis){
console.log("withThis", withThis);
}
// Capture the function so we can remove it later.
var storeFunc = addListenerWithArgs(someElem, "click", doSomething, "foo");
// To remove the listener, use the normal routine:
someElem.removeEventListener("click", storeFunc);

There is a special variable inside all functions: arguments. You can pass your parameters as anonymous parameters and access them (by order) through the arguments variable.
Example:
var someVar = some_other_function();
someObj.addEventListener("click", function(someVar){
some_function(arguments[0]);
}, false);

I was stuck in this as I was using it in a loop for finding elements and adding listner to it. If you're using it in a loop, then this will work perfectly
for (var i = 0; i < states_array.length; i++) {
var link = document.getElementById('apply_'+states_array[i].state_id);
link.my_id = i;
link.addEventListener('click', function(e) {
alert(e.target.my_id);
some_function(states_array[e.target.my_id].css_url);
});
}

I suggest you to do something like that:
var someVar = some_other_function();
someObj.addEventListener("click", (event, param1 = someVar) => {
some_function(param1);
}, false);

The PERFECT SOLUTION for this is to use Closures like this:
function makeSizer(size) {
return function () {
document.body.style.fontSize = `${size}px`;
};
}
//pass parameters here and keep the reference in variables:
const size12 = makeSizer(12);
const size24 = makeSizer(24);
const size36 = makeSizer(36);
document.getElementById('size-12').addEventListener("click", size12);
document.getElementById('size-24').addEventListener("click", size24);
document.getElementById('size-36').addEventListener("click", size36);
document.getElementById('remove-12').addEventListener("click", ()=>{
document.getElementById('size-12').removeEventListener("click", size12);
alert("Now click on 'size 12' button and you will see that there is no event listener any more");
});
test<br/>
<button id="size-12">
size 12
</button>
<button id="size-24">
size 24
</button>
<button id="size-36">
size 36
</button>
<button id="remove-12">
remove 12
</button>
So basically you wrap a function inside another function and assign that to a variable that you can register as an event listener, but also unregister as well!

Also try these (IE8 + Chrome. I dont know for FF):
function addEvent(obj, type, fn) {
eval('obj.on'+type+'=fn');
}
function removeEvent(obj, type) {
eval('obj.on'+type+'=null');
}
// Use :
function someFunction (someArg) {alert(someArg);}
var object=document.getElementById('somObject_id') ;
var someArg="Hi there !";
var func=function(){someFunction (someArg)};
// mouseover is inactive
addEvent (object, 'mouseover', func);
// mouseover is now active
addEvent (object, 'mouseover');
// mouseover is inactive
Hope there is no typos :-)

The following answer is correct but the below code is not working in IE8 if suppose you compressed the js file using yuicompressor. (In fact,still most of the US peoples using IE8)
var someVar;
someVar = some_other_function();
alert(someVar);
someObj.addEventListener("click",
function(){
some_function(someVar);
},
false);
So, we can fix the above issue as follows and it works fine in all browsers
var someVar, eventListnerFunc;
someVar = some_other_function();
eventListnerFunc = some_function(someVar);
someObj.addEventListener("click", eventListnerFunc, false);
Hope, it would be useful for some one who is compressing the js file in production environment.
Good Luck!!

var EV = {
ev: '',
fn: '',
elem: '',
add: function () {
this.elem.addEventListener(this.ev, this.fn, false);
}
};
function cons() {
console.log('some what');
}
EV.ev = 'click';
EV.fn = cons;
EV.elem = document.getElementById('body');
EV.add();
//If you want to add one more listener for load event then simply add this two lines of code:
EV.ev = 'load';
EV.add();

The following approach worked well for me. Modified from here.
function callback(theVar) {
return function() {
theVar();
}
}
function some_other_function() {
document.body.innerHTML += "made it.";
}
var someVar = some_other_function;
document.getElementById('button').addEventListener('click', callback(someVar));
<!DOCTYPE html>
<html>
<body>
<button type="button" id="button">Click Me!</button>
</body>
</html>

Since your event listener is 'click', you can:
someObj.setAttribute("onclick", "function(parameter)");

Another workaround is by Using data attributes
function func(){
console.log(this.dataset.someVar);
div.removeEventListener("click", func);
}
var div = document.getElementById("some-div");
div.setAttribute("data-some-var", "hello");
div.addEventListener("click", func);
jsfiddle

The following code worked fine for me (firefox):
for (var i=0; i<3; i++) {
element = new ... // create your element
element.counter = i;
element.addEventListener('click', function(e){
console.log(this.counter);
... // another code with this element
}, false);
}
Output:
0
1
2

You need:
newElem.addEventListener('click', {
handleEvent: function (event) {
clickImg(parameter);
}
});

Develop Reference

JavaScript is the programming language of the Web.

jQuery handler not defined (handler.guid) - javascript

Related

Probably a really simple thing but I can't seem to pass an argument into my Javascript function [duplicate]

Attaching different eventListeners for each item in for-of-loop [duplicate]

probably moronic js syntax error. Object is null

jQuery binding function on focus

How to pass arguments to addEventListener listener function?

Categories

Resources