<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head>
<meta http-equiv="Content-type" content="text/html; charset=utf-8" />
<title>test</title>
</head>
<body>
<script type="text/javascript" charset="utf-8">
(function(){
// this
var test=function(){
//this
return function(){
//this
};
}
(function(){
//this
var a={
p1:function(){
//this
}
};
})();
})();
</script>
</body>
</html>
views:
218answers:
3
+1
A:
other than this being a comment
In a scope chain sense it will move from the this in the bottom function all the way back to the global this.
e.g the this in
p1:function(){
//this
}
then the this above it
(function(){
//this
var a={
p1:function()
Then the this above it
(function(){
// this
var test=function(){
There is a good presentation by Nicholas Zakas at Yahoo on it at http://www.youtube.com/watch?v=mHtdZgou0qU
AutomatedTester
2009-07-13 10:31:01
+2
A:
The meaning of this depends on how the function containing it was called, not how it was constructed.
There is an excellent explanation of how it works in JavaScript: The Good Parts.
The short version is that, when you call a function (m) as the method of an object (o), then this is o.
var o = {
m: function () {
return this;
}
}
var foo = {
bar: o.m;
}
o === o.m();
foo === foo.bar();
David Dorward
2009-07-13 10:34:12
+6
A:
David Dorward already mentioned about JavaScript: The Good Parts by Douglas Crockford.
From Section 4.3 of that excellent book:
Invoking a function suspends the execution of the current function, passing control and parameters to the new function. In addition to the declared parameters, every function receives two additional parameters: this and arguments. The this parameter is very important in object oriented programming, and its value is determined by the invocation pattern. There are four patterns of invocation in JavaScript: the method invocation pattern, the function invocation pattern, the constructor invocation pattern, and the apply invocation pattern. The patterns differ in how the bonus parameter this is initialized.
Crockford continues to explains the binding of 'this' in each of these patterns, as follows:
The Method Invocation Pattern: When a function is stored as a property of an object, we call it a method. When a method is invoked, this is bound to that object.
The Function Invocation Pattern: When a function is invoked with this pattern, this is bound to the global object. This was a mistake in the design of the language.
The Constructor Invocation Pattern: If a function is invoked with the new prefix, then a new object will be created with a hidden link to the value of the function's prototype member, and this will be bound to that new object.
The Apply Invocation Pattern: The apply method lets us construct an array of arguments to use to invoke a function. It also lets us choose the value of this. The apply method takes two parameters. The first is the value that should be bound to this. The second is an array of parameters.
Vijay Dev
2009-07-13 11:27:27