JavaScript function declaration

javascript function-declaration
Anand Shah picture Anand Shah · Dec 8, 2009 · Viewed 20.1k times · Source

Are the JavaScript code snippets given below some sort of function declaration? If not can someone please give an overview of what they are?

some_func = function(value) {
    // some code here
}

and

show:function(value){
   // some code here
}

Answer

Justin Johnson picture Justin Johnson · Dec 8, 2009

There are six ways/contexts in which to create functions:

1) Standard declarative notation (most familiar to people with C background)

function foo() {}

All the rest are function expressions:

2) As a method of an object literal

var obj = {
    foo: function() {}
};

3) As a method of an instantiated object (created each time new is exectued)

var Obj = function() {
    this.foo = function() {};
};

4) As a method of a prototype (created only once, regardless of how many times new is executed)

var Obj = function() {};
Obj.prototype.foo = function() {};

5) As an anonymous function with a reference (same effect as #1) *

var foo = function() {};

6) As an immediately executed anonymous function (completely anonymous) 

(function() {})();

* When I look at this statement, I consider the result. As such, I don't really consider these as anonymous, because a reference is immediately created to the function and is therefore no longer anonymous. But it's all the same to most people.

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