Closure and LexicalEnvironment

   
• Each variable on create get [[Scope]] - link on object in context where it was created
   
• [[Scope]] - is private internal property of function
   
• On function call: create a new object with LexicalEnvironment's (LE) variables. This object get link on external object from [[Scope]]
   
• Searching variables: at first it search in current variable's object and then by link [[Scope]]

Example

function saySomething(text) {
   // LexicalEnvironment = {sign: undefined}
   var sign = '!!!';
   // LexicalEnvironment = {sign: '!!!'}
   console.log('I say ' + text);

   function getText(text) { // [[Scope]] -> {sign: '!!!'}
      return text;
   }
}
saySomething('Hello World');

Where:

saySomething.[[Scope]] = window

getText.[[Scope]] = variable's object of current saySomething() call.