Question

I’m coming across these two ways of declaring functions in Javascript.

One is an assignment expression that to declares foo to be whatever the function returns, i.e.

var foo = function(){

//do something
};

And the other way of declaring a function seems to make it a property of a larger object:

foo: function() { //do something }

I’m assuming you would use the second form when you needed to access that function in an object context, i.e.:

myobject.foo();

What is the proper name for the second form?

Answer 1

The following:

var foo = function(){
  //do something
}; 

the right hand side is a FunctionExpression, it is different to a FunctionDeclaration in that the function isn’t created until the code is executed, which is after function declarations have been processed and variable instatiation has occurred.

It is not a function declaration.

> foo: function() {
>  //do something
> }

that is also a function expression, to put it in the same form as the first:

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

and it too is only created when the code is executed. There is no practical difference between the two above, use whatever seems best.

Edit

Oh, and in a function expression, the name is optional (and generally recommended against because of issues with IE and named function expressions).