JS Scope and variable elevation

Function declarations and variable declarations is always moved ("hoisted") invisibly to the top of their containing SCOP E by the JavaScript interpreter.

Example1:

    var foo = 1;     function Bar () {      if (!  Foo) {        var foo = ten;      }       // Ten     }    Bar ();

Example2:

    var a = 1;     function B () {      = ten;       return ;       function A () {}    }    b ();     // 1

Example3:

    var x = 1;     // 1    if (true) {      var x = 2;       // 2     }    //  2

Example4:

  function foo () {      var x = 1;       if (x) {        (function  () {          var x = 2;           // Some other code         } ());      }       // x is still 1.    }

Named Function Expressions

You can give names to functions defined on function expressions, with syntax like a function declaration. This does does it a function declaration, and the name is not brought to scope, nor is the body hoisted. Here's some code to illustrate what I mean:

Example 5:

Foo ();//TypeError "Foo is not a function"Bar ();//validBaz ();//TypeError "Baz is not a function"Spam ();//referenceerror "spam is not defined"    varFoo =function() { };//anonymous function expression (' foo ' gets hoisted)    functionBar () {};//function declaration (' Bar ' and the function body get hoisted)    varBaz =functionSpam () {};//named function expression (only ' Baz ' gets hoisted)foo ();//validBar ();//validBaz ();//validSpam ();//referenceerror "spam is not defined"

Example 6:

   // 5    var function () {Console.log (4);};     function getName () {Console.log (5);};    GetName (); // 4

Example 7:

    functionFoo () {getName=function() {Console.log (1);      }; return  This; } foo.getname=function() {Console.log (2);    }; Foo.prototype.getName=function() {Console.log (3);    }; varGetName =function() {Console.log (4);    }; functionGetName () {Console.log (5);    }; Foo.getname (); //2GetName ();//4Foo (). GetName ();//1GetName ();//1    NewFoo.getname ();//2    NewFoo (). GetName ();//3    New NewFoo (). GetName ();//3

JS Scope and variable elevation