Revision f5a071d1-c0c0-4371-a8d2-c78ea4b9df28 - Stack Overflow

The first one (function doSomething(x)) should be part of an object notation.

The second one (`var doSomething = function(x){ alert(x);}`) is simply creating an anonymous function and assigning it to a variable, `doSomething`. So doSomething() will call the function.

You may want to know what a *function declaration* and *function expression* is.

A function declaration defines a named function variable without requiring variable assignment. Function declarations occur as standalone constructs and cannot be nested within non-function blocks.

 function foo() {
 return 3;
 }

> ECMA 5 (13.0) defines the syntax as <br/>
> function Identifier ( FormalParameterList<sub>opt</sub> ) { FunctionBody }

In above condition the function name is visible within its scope and the scope of its parent (otherwise it would be unreachable).

And in a function expression

A function expression defines a function as a part of a larger expression syntax (typically a variable assignment ). Functions defined via functions expressions can be named or anonymous. Function expressions should not start with “function”.

 // Anonymous function expression
 var a = function() {
 return 3;
 }

 // Named function expression
 var a = function foo() {
 return 3;
 }

 // Self-invoking function expression
 (function foo() {
 alert("hello!");
 })();

> ECMA 5 (13.0) defines the syntax as <br/>
> function Identifier<sub>opt</sub> ( FormalParameterList<sub>opt</sub> ) { FunctionBody }