What is scope in javascript

javascript-scope.js

/**
* In JavaScript there are only 2 scopes, one is global scope and the other is Function scope. 
* In Ecma Script 5 they have introduced 'let' variable which has lexical scope also. 
*/

/*
* In below example log method has 2 things in scope one is global variable 'message' and the other is local variable 'prefix'
*/
var message = "hello world";
function log() {
  var prefix = "Logger: ";
  alert(prefix + message);
}