JavaScript function declaration

Question

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         


        

Answer 1

One way of doing it:

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

Another way:

function some_funct() {
}

Yet another way:

var some_object={};
some_object["some_func"] = function() {};

or:

var some_object={};
some_object.some_func = function() {};

In other words, they are many ways to declare a function in JS.

---

Your second example is not correct.

Answer 2

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.

Answer 3

The first one is simply creating an anonymous function and assigning it to a variable some_func. So using some_func() will call the function.

The second one should be part of an object notation

var obj = {
  show:function(value){
    // some code here
  }
};

So, obj.show() will call the function

In both cases, you are creating an anonymous function. But in the first case, you are simply assigning it to a variable. Whereas in the second case you are assigning it as a member of an object (possibly among many others).

Answer 4

The first one...

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

is declaring a variable and assigned an anonymous function to it, which is equivalent to...

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

The second one should look like this...

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

and equivalent to...

//pseudo code
class MyClass {
    function show (value) {
        // some code here
    }
}
obj = new MyClass();    // obj.show(value)

Cheers

Answer 5

They are called anonymous functions; you can read more about them here:

http://www.ejball.com/EdAtWork/2005/03/28/JavaScriptAnonymousFunctions.aspx

Answer 6

The first one is a function declaration assigned to a variable (at least it should be, despite the fact that it's missing the variable type declaration first), the second one is probably related to a object declaration.