This is some JS code
var methodArr = ['firstFunc','secondFunc','thirdFunc'];
for(var i in methodArr)
{
window[methodName] = function()
{
console.log(methodName);
}
}
My problem is that how to get the name of a function in JS.
In JS, use this.callee.name.toString() can get the function name. But in this situation, it is a null value. How can i get the 'funName' string?
Sorry, I didn't make it clear.
I want to create functions in a for loop, all these functions has almost the same implementation which need its name. But others can call these functions use different name.I want to know what methodName function is called.
it seems a scope problem.
Try this:
var methodArr = ['firstFunc','secondFunc','thirdFunc'];
for(var i in methodArr) {
var methodName = methodArr[i]; // <---- this line missed in your code?
window[methodName] = (function(methodName) {
return function() {
console.log(methodName);
}
})(methodName);
}
window['secondFunc'](); // output: secondFunc
Related
I've got a functional script on my site that allows me to open a link in a new window when a specific class is added to the link. I need a lot of those on my site though so I figured I'd make the script a bit easier to edit by working with variables.
In the process of changing out hardcoded strings for variables my script stopped working though. The only one that works is the var where I set the url.
I'm learning that ${} doesn't work everywhere. Hope that someone can point out where my thinking is wrong. Also hope that I got the terminology right, trying to learn though! :-)
var function1Name = "test_function";
var function1Url = "https://www.google.com";
var function1Class = ".test_function_class";
function ${function1Name}() {
window.open(function1Url, "_blank", "height=200");
}
jQuery("${function1Class}").click(function(){
${function1Name}()
});
None of your uses of ${} are valid JavaScript syntax.
Your function declaration van be replaced with:
window[function1Name] = function () {
window.open(function1Url, "_blank", "height=200");
}
Please note that the function will no longer be hoisted when declared this way, so order of operation matters.
The click handler can be written as follows:
jQuery(function1Class).click(function() { // Note that I just used the variable there.
window[function1Name]();
});
There is a ${} concept in JavaScript, but that is only in template literals:
const myVariable = "Foo";
const message = `myVariable contains: "${myVariable}"!`;
console.log(message);
There's several syntax issues here.
Firstly, function ${function1Name}() is not valid syntax. Function names must be defined before runtime. If you want to dynamically access a function, place it in an object and set the key with the variable reference.
Secondly, ${function1Name}() is again not valid syntax. You cannot invoke a function like that dynamically. Referring to the suggestion above, you can access an object dynamically so the first point fixes this problem.
Thirdly, string interpolation only works within template literals, so you need to delimit the string with backticks: ``. However it's completely redundant here as you can just use $(function1Class)
With those issues in mind, here's an updated example:
var function1Name = "test_function";
var function1Url = "https://www.google.com";
var function1Class = ".test_function_class";
var funcObj = {
[function1Name]: function() {
console.log(`function called, window would open here containing ${function1Url}...`);
// window.open(function1Url, "_blank", "height=200");
}
}
$(function1Class).click(function() {
funcObj[function1Name]()
});
/*
alternative using a template literal, although note that it's redundant here
$(`${function1Class}`).click(function() {
funcObj[function1Name]()
});
*/
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
Click me
One last thing to note is that no version of IE supports template literals, so be sure of your browser support requirements before using them.
So cool, I got it to work!
var function1Name = "test_function_1";
var function1Url = "https://www.google.com";
var function1Class = ".test_function_class1";
var function2Name = "test_function_2";
var function2Url = "https://www.cnn.com";
var function2Class = ".test_function_class2";
// Function 1
window[function1Name] = function () {
window.open(function1Url, "_blank", "toolbar=no,status=no,scrollbars=yes,resizable=yes,top=500,left=500,width=600,height=745");
}
jQuery(function1Class).click(function() {
window[function1Name]();
});
// Function 2
window[function2Name] = function () {
window.open(function2Url, "_blank", "toolbar=no,status=no,scrollbars=yes,resizable=yes,top=500,left=500,width=600,height=745");
}
jQuery(function2Class).click(function() {
window[function2Name]();
});
I can now add a bunch of url's and corresponding classes as was my intention. Super happy about that.
A follow up question though, as I'll have to experiment with what the ideal window parameters will be I'm trying to make those arguments variables as well. I've tried the examples of how to insert a variables output from the functional code but those methods don't work there. Here's that code:
var windowWidth = 250
var function1Name = "test_function_1";
var function1Url = "https://www.google.com";
var function1Class = ".test_function_class1";
var function2Name = "test_function_2";
var function2Url = "https://www.cnn.com";
var function2Class = ".test_function_class2";
// Function 1
window[function1Name] = function () {
window.open(function1Url, "_blank", "toolbar=no,status=no,scrollbars=yes,resizable=yes,top=500,left=500,width=[windowWidth],height=745");
}
jQuery(function1Class).click(function() {
window[function1Name]();
});
// Function 2
window[function2Name] = function () {
window.open(function2Url, "_blank", "toolbar=no,status=no,scrollbars=yes,resizable=yes,top=500,left=500,width=600,height=745");
}
jQuery(function2Class).click(function() {
window[function2Name]();
});
How would I insert the variables value (2nd line of Function1) there ?
I want to merge a argument of a function with a variable
But i don't know how to do that.
firstDates = [];
function myFunction(partOne) {
partOne + Dates.push(someOtherVar);
}
myFunction(first);
I know that this not works, but what would be the right way?
why not something like this?
var dates = {};
function myFunction(partOne) {
dates[partOne] = []; // dates["first"] = []
dates[partOne].push(someOtherVar); // dates["first"].push(someOtherVar)
}
myFunction("first");
Otherwise what you are trying to accomplish is an eval type of set up. This is generally a very bad idea. Don't use dynamically named variables.
I'm working on a code where I must pass a different function to some objects.
In this case, I'm trying to pass a different function for the onchange event. So currently what I got is something like this this:
var ArrayList; //Contains some data to use with ObjectArray format { n: data }
var ObjectArray; //Contains several objects format Array[n] = Object;
for(var key in ArrayList){
var doFunction = function() {
Object[key].doSomething(ArrayList[key]);
}
Object[key].onchange = doFunction;
}
The problem here I believe is that I'm afraid it will execute the code as it is declared and not with the values of the actual variables.
Is there a way to pass the function with the values as it executes? or will the variables get parsed the way its written?
It's the classic function in a loop problem. You need to understand how closures work.
Read the "Example 3" part of this answer carefully. The whole How do JavaScript closures work? question, too.
Another example that might help understand intuitively:
var key = 5;
var onchange = function () {
console.log(key);
};
onchange(); // 5
key = 10; // the loop reassigns the key on each iteration
onchange(); // 10
This is how it should be done:
var ArrayList; //Contains some data to use with ObjectArray format { n: data }
var ObjectArray; //Contains several objects format Array[n] = Object;
for(var key in ArrayList)
{
(function(key)
{
var doFunction = function()
{
Object[key].doSomething(ArrayList[key]);
}
Object[key].onchange = doFunction;
}(key))
}
My problem is pretty easy to understand. I have a JSON object (see code) and I will automatically call all functions of this object in the order that those appears. .
var installer = {
a : function() {
...
}
b : function() {
...
}
};
for(var func in installer) {
fn.call(document);
};
Have you any idea why the previous code doesn't work ? I'm sorry, I'm a beginner in javascript.
Thanks in advance !
Regards.
You don't have a variable called fn, and you are also missing commas at the end of your function definitions.
Additionally, your functions will not be called in order because JavaScript orders your object properties arbitrarily. You may want to consider using an array or, as I have done below, specify an array that determines the order.
var installer = {
a : function() {
...
},
b : function() {
...
},
};
var order = [ "a", "b" ];
for(var i = 0; i < order.length; i++) {
installer[order[i]].call(document);
}
You declare var func as the variable to loop through the members of installer, yet you use fn.call(...). Where did fn come from?
Should you be able to do: installer[func].call(document) instead of fn.call(document).
Also your functions declared in the installer object don't take any arguments, yet you're passing document as an argument.
[updated code to add missing .call to installer[func](document)]
I'm trying to create a simple, small and basic javascript framework just for learning purposes.
But the thing is that i'm allready stuck at the very basics.
I'm trying to do something like this:
$('testdiv').testFunction();
And the code i've written for that:
var elementID;
var smallFramework = {
$:function(id) {
this.elementID = id;
},
testFunction:function() {
alert(this.elementID);
}
};
window.$ = smallFramework.$;
But in return I get:
$('testdiv) is undefined
Can anyone help me with this small and hopefully easy question?
To get the behavior you're expecting, you need the $ function to return an object with a method named testFunction.
Try:
var smallFramework = // an object for namespacing
{
$:function(id) // the core function - returns an object wrapping the id
{
return { // return an object literal
elementID: id, // holding the id passed in
testFunction: function() // and a simple method
{
alert(this.elementID);
}
};
}
};
Of course, there are many other ways to achieve the behavior you desire.
If you're trying to add methods to an HTML element you could do something along these lines.
$ = function( elementId ) {
var element = document.getElementById( elementId );
element.testFunction = function(){
alert( this.id );
return this; // for chaining
}
return element;
}
$('test').testFunction();
Try
smallFramework.$('testdiv');
instead. According to the code you posted, that's where your $ function ended up.
Or alternatively, it looks like you're trying to replicate something like jQuery. You might want to try something like this.
var $ = smallFramework = (function () {
var f =
{
find:function(id) {
f.elementID = id;
return f; //every function should return f, for chaining to work
},
testFunction:function() {
alert(f.elementID);
return f;
}
}
return f.find //the find function will be assigned to $.
//and also assigned to smallFramework.
//the find function returns f, so you get access to testFunction via chaining
// like $("blah").testFunction()
})() //note this function gets called immediately.
this code may look confusing to someone new to JavaScript because it depends heavily on the concept of closures. I suggest that if this doesn't make sense, spend some time at Douglas Crockford's JavaScript website. This is important because the code above will bite if you happen to use this in the find function because this won't be bound to f, as you may expect it to be when you use it from $ or smallFramework.