Develop Reference

Add event listener of a method present in another js file

I am accessing few methods written in another js file. So i'm accessing them like this:
file1:
function minit() {
this.addval = function(val1, val2) {
return val1 + val2;
}
function autoexecute(d) {
//do something here//
//raise event//
}
};
file2:
var con = new minit();
var result = con.addval(2, 3);
/*
con.autoexecute(function(d) { //Wanna do something like this
alert(d);
});
*/
Above things are working as expected, getting result..
Now, Suppose autoexecute(d) method is invoking automatically after a time interval. How can i know if the method is executed ?
So that, I want to create an event(in file2) of autoexecute(d)(in file1).
UPDATE:
I hope this example will help you to understand the issue..
company.js //this is the main file which will be used as a reference in ui.html
function hello(personname) { //this method will invoke automatically after 1 minute..
}
ui.html
<script src="company.js"></script>
<script>
$(document).ready(function() {
function bye(personame) { //this method will be called automatically if hello method invoked.... personame is the argument passed from hello method//
alert("comany.js -> hello function is executed");
}
});
</script>

You can only do this if the functions have the same scope (global scope is the best case scenario). If the autoexecute function has local scope then you cannot to do it.
In essence, override the original function like this...
// keep a reference to the original function
var _autoexecute = autoexecute;
// override the original function with your new one
function autoexecute(d) {
alert("before autoexecute"); // fired before the original autoexecute
_autoexecute(d); // call the original autoexecute function
alert("after autoexecute"); // fired after the original autoexecute
}
Now, whenever autotexecute is called it will call your new function which can handle both before and after events, as well as calling the original function. Just remove the (horrible) alerts and replace with event handlers as required.

To my knowledge, and someone should correct me if I am wrong, there is no way (at least without some library) to detect a function being fired in javascript. Function executions do not fire an event that other functions can 'handle' in that that sense.
In your example you wanted a function to automatically fire after the other function has fired, all you need to do is call the function you want to fire at the end of the one that was "fired" in the first place. Confusing but hope this helps.
function handler(){
alert("main function was fired!");
}
function main(){
//Code of main goes here and then at the end just add:
handler();
}
Now when your "main" has finished its work it will call upon the handler function.
Regardless of where you define the handler function, which can be a different file or same file, so long as it is reachable from within the main's scope, it will be fired at the end of it. It can even be declared after main has been declared, so long as it is declared before main is fired.

Javascript - Return in a function parameter another function

What i'm trying to do might sound simple.
I just need to make a callback with another function
Here is an example using jQuery.
(function ( $ ) {
"use strict";
var colors;
colors = function(col){
return col;
};
$(document).ready(function(){
colors(function(){alert('Orange');});
});
})(jQuery);
So when the document be ready, i need to send an alert that says 'Orange' but i want to do it by returning a function.
If you know another way to do it please let me know.

To call a function, you have to put () after it. Since colors() returns the function, put () after the call to colors:
$(document).ready(function(){
colors(function(){alert('Orange');})();
});
More generally, the way you deal with callbacks is something like:
callback = getCallback(args);
callback();

Having to use $(document).ready() multiple times in same script

I have a script with the following structure:
Test = {
CONSTANTS : {},
VARIABLES : {},
MARKUP : {},
FUNCTIONS : {
init : function () {
// Access variable from different namespace
var all_constants = DifferentNamespace.CONSTANTS; // WORKS
var tester = DifferentNamespace.CONSTANTS.chunk_of_markup; // SAYS UNDEFINED
}
},
init : function () {
// Call real init() function
$(document).ready(function () {
Test.FUNCTIONS.init();
});
}
};
$(document).ready(function () {
Test.init();
});
If I remove either of the $(document).ready(..) function calls, when I try to access a constant from a different namespace it is undefined; with both is works well.
As you can see I'm using two init() functions, one it just to neaten up the call to init because I have wrapped functions inside an additional object.
If I remove the function that is on the same level as CONSTANTS, VARIABLES etc and try to call the init() within Test.FUNCTIONS it still does not work.
Edit:
If i console.log(all_constants) I get the full object (with .chunk_of_markup) but if I console.log(tester) is get undefined. If i wrap tester i get []
I should also note that the other namespace gets the markup from a seperate file.
Any ideas why?

Having two document ready doesn't make a difference here. You could have one document.ready and/or call Test.FUNCTIONS.init directly and all should work, and the fact that they are in different namespaces doesn't matter as well.
As for why you're getting undefined, I think it is probably because your chunk_of_markup variable is actually undefined at that point. My guess is that you're getting the value for it through AJAX and so the call is done asynchronously which means the DOM will be ready before it actually returns a value. When you use the Debugger then the value is evaluated at the point of time where you run the command so by then, the async call already returns successfully (it's a race condition, if you're fast enough and your AJAX is slow then you can still get undefined, and it's also why 2 ready functions happen to make it slow enough for the AJAX call to return but it's still unreliable).
In all cases, if my theory is correct, then you need to hook to the callback of the AJAX request rather that DOM ready event, this is the only place where you can guarantee that your variable is defined.

Why not call the function init() in the document Handler itself.. I don't think that will lead to the same problems.. You can remove the Test.init() completely as it does not seem to do anything in here
Test = {
CONSTANTS : {},
VARIABLES : {},
MARKUP : {},
FUNCTIONS : {
init : function () {
// Access variable from different namespace
var all_constants = DifferentNamespace.CONSTANTS; // WORKS
var tester = DifferentNamespace.CONSTANTS.chunk_of_markup; // SAYS UNDEFINED
}
}
};
$(document).ready(function () {
Test.FUNCTIONS.init();
});

javascript anonymous function parameter passing

I have some javascript code (within an object) :
toggle: function() {
var me = this;
var handler = function() { me.progress() };
me.intervalId = setInterval(handler, me.intervalTime);
//...More code
}
I'm kind of new to javascript, so doing the above as far as I can tell actually passes the me variable into anonymous the function. I was wanting to see if there is a more declarative way to do so? I wanted something along the line of:
var handler = (function(o) { o.progress();})(this));
but that doesn't seem to be working... Am I missing something? Is this a case where "this is the way the language works so just declare a local variable and deal with it"?
UPDATE:
The source to my problem was/is my unclear understanding of scope and closures in javascript. I found this article to help me understand a little more.

You can use ".bind()":
var handler = function() { this.progress(); }.bind(this);
New browsers have "bind()", and the Mozilla docs have a solid implementation you can use to patch older browsers.

The reason
var handler = (function(o) { o.progress();})(this));
doesn't work because it just immediately calls the anon function, therefore immediately calling o.progress() and assigns the return value of the anon function (undefined) to handler. You need to return an actual function from the outer function:
handler = (function(me){
return function(){
return me.progress();
}
}(this));
On the flip side this is equivalent and just as bad looking as bad looking as the variable assignment (but can still be useful, particularly if this needs to be done in a loop, with the changing i rather than the fixed this).
BTW, if the progress function doesn't have any calls to this inside it , just doing handler = this.progress (without the parens) might suffice.

The anonymous function has access to me because it is declared inside of the outer function (the toggle function); it is closed over by the outer function.
Your handler function will be called by setInterval, which passes exactly zero arguments. This means you can't use parameters in the handler function itself.
I you really want to pass me explicitly, you could write a function accepting an parameter, and have that function return an anonymous function without parameters, but which could access the creator function's parameter:
toggle: function() {
var me = this;
var handler = (function (o) { return function() { o.progress() }; })(me);
me.intervalId = setInterval(handler, me.intervalTime);
//...More code
}
But this basically adds a layer of redirection without really making it more legible. Unless you pull that creating function outside:
function createProgressHandler(o) {
return function() {
o.progress();
};
}
// ...
toggle: function() {
var me = this;
var handler = createProgressHandler(me);
me.intervalId = setInterval(handler, me.intervalTime);
//...More code
}

What you have there is a closure. The function that is created and assigned to handler keeps a reference to the me object. This is normal, everyday JavaScript, and that's the way that closures work generally.

Have you tried to return the function like this?
var handler = function(o){
return function(){
o.progress();
}
}(me);
Now you can call:
handler();

Calling a function in javascript object literal notation declaration

I'm trying to call a function within an object literal that I created, using the this keyword. But an error shows up saying this.doTheMove() is not a function:
window.onload = function(){
var animBtn = document.getElementById('startAnim');
animBtn.addEventListener('click', Animation.init, false);
}
var Animation = {
init: function(){
this.doTheMove(); // I'm calling the function here, but it gives an error.
},
doTheMove: function(){
alert('Animation!');
}
}
Why is there an error?

An explanation of what's happening. Pointy's answer is good but I want to explain it more generically. A very good research on this can be found here
An event handler is just a callback. You pass it a function and an event to listen on. Interally all it will do is call that function.
Animation.init is just a getter for that function. Think of it like this:
var callback = Animation.init
animBtn.addEventListener('click', callback, false);
...
// internal browser event handler
handler() {
// internal handler does stuff
...
// Oh click event happened. Let's call that callback
callback();
}
So all you've done is passed in
var callback = function(){
this.doTheMove(); // I'm calling the function here, but it gives an error.
}
By default in javascript this === window. This will refer to the global object if it isn't set to something. The net effect is that window.doTheMove is called. And that function doesn't exist.
In this case since callback is actaully called by an event handler the this object points at the DOM object that triggered the event so your calling node.doTheMove which still doesn't exist.
What you wanted to do is wrap it with a reference to Animation.
var callback = function() {
Animation.init();
}
This is a function execution and it executes init on Animation. When you execute it on an object like that then internally this === Animation as you would expect.
To sum up. The issue here is that Animation.init is just a reference to a function. It has no information about anything else like Pointy mentioned.

You have to change the way you set that up:
window.onload = function(){
var animBtn = document.getElementById('startAnim');
animBtn.addEventListener('click', function() { Animation.init(); }, false);
}
In JavaScript, the fact that a function happens to be defined as part of an object literal really doesn't mean very much (if anything, in fact). The reference to Animation.init does get you to the proper function, but the problem is that when the function is later invoked (in response to an actual "click"), the browser calls the function but has no idea that the object "Animation" should be the this reference. Again, the fact that the function was declared as part of the object is of no importance at all here. Therefore, if you want this to be something in particular of your own choosing, then you have to make sure it's set explicitly in code you control. The solution above is about the simplest way to do it: it handles the "click" events with an anonymous function that does nothing other than invoke the "init" function via an explicit reference through "Animation". That will ensure that this refers to the "Animation" object when "init" runs.
Another alternative would be to use the ".bind()" facility that some browsers and frameworks support:
window.onload = function(){
var animBtn = document.getElementById('startAnim');
animBtn.addEventListener('click', Animation.init.bind(Animation); }, false);
}
The net effect is almost exactly the same: that call to ".bind()" returns a function that invokes the function on which it was called (that being the "init" function in the "Animation" object), and does so with its first argument as the this reference (the "context" object). That's the same thing that we get from the first example, or effectively the same anyway.

Here's another nice approach, I think.
window.onload = function(){
var animBtn = document.getElementById('startAnim');
animBtn.addEventListener('click', Animation.init, false);
};
var Animation = {
init: function(){
Animation.doTheMove(); // This will work, but your IDE may complain...
},
doTheMove: function(){
alert('Animation!');
}
};

You might want to use the portotype base approach:
// generate a prototype object which can be instantiated
var Animation = function() { this.doTheMove(); }
Animation.prototype.doTheMove = function() {
// if the object has only one method, the whole code could be moved to
// var Animation = function() {...} above
alert('Animation!');
}
Animation.prototype.otherMethod = function(param1, param2) {
// ...
}
// run the code onload
window.onload = function(){
var animBtn = document.getElementById('startAnim');
animBtn.addEventListener('click', new Animation(), false);
}

Six and a half years later, but I'm hoping my answer can also provide some insight for current and future developers.
I tend to code using literal objects inside of self defined functions, and the original question posted works just fine if another self-executing function is added along with a try and catch statement.
It's very important to point out that it's all about scope and context.
Please correct any drawbacks or provide more effective suggestions of using this method.
(function() {
console.log(this); // window object
var animation = {
init: function() {
this.doTheMove();
},
doTheMove: function() {
alert("Animation");
console.log(animation); // animation object
}
};
(function() {
try {
console.log("animation.init"); // animation.init function
animation.init();
} catch(e) {
console.log("Error is: " + e);
}
})();
})();