I am creating a object in javascript like this
function myobject() {
this.myvar1 = 0;
this.myvar2 = 0;
}
myobject.prototype.a = function(){
this.myvar1 +=1;
$('#button').click(function () { // 'this' is undefined
alert(this.myvar1)
})
}
var mything = new myobject();
mything.a()
What is the proper way to pass the this pointer to an anonymous function?
For updated question:
The issue is that inside that event handler, this refers to the element you clicked on, rather than your myobject, so just keep a reference to it, like this:
myobject.prototype.a = function(){
this.myvar1 +=1;
var self = this;
$('#button').click(function () {
alert(self.myvar1)
});
}
For previous question: What you have should work (exactly as you have it), you can test it here.
this is undefined, it just refers to the handler inside that function, just maintain a reference like this: jsfiddle.net/nick_craver/6LtacAdding the following code to the end of your snippet and running it correctly alerts '1':
mything.b();
alert(mything.myvar1);
What were you expecting? Perhaps you're incorrectly invoking mything.b() ?
To pass this to an inner function, "save" it to another variable.
myobject.prototype.a = function() {
var self = this;
self.myvar1 += 1;
$('#button').click(function () {
alert(self.myvar1);
});
}
What's happening here is that jQuery is hijacking the value of this in the anonymous function used as a handler for the click event. It's kind of confusing, but jQuery's behavior is to assign the DOM element that triggered the event to this. There are a couple ways to set the value of this explicitly (the "context") for the callback function:
I wrote a couple posts on my blog that explain these in more detail if you're interested:
In both cases, since this will now be your object and not the triggering DOM element, you can get the triggering DOM element by inspecting the event object, which will be the second parameter to your callback function.
Others here have done a nice job explaining the issue and how to resolve without adding any dependencies, but personally I think this plugin is a better overall solution (if you don't mind the dependency):
