Interesting Quirkly Javascript Questions Collection (Planed to be used for interview)

js_questions.js

/* ================== */

/**
 * Concepts:
 *   Global Context
 *   Chained Assignment
 */
var x = 1;
var y = 2;
var z = 3;
!function init() {
  var x = y = z = 10;
}()

alert(x); // 1
alert(y); // 10
alert(z); // 10

/* ================== */

/* 
 * Concepts:
 *   Scope Chain
 *   Object
 *   Prototype Chain
 */
var foo = function () {},
    bar = function () {
      this.a = '1';
    };
foo.prototype.a = '2';

function main() {
  foo.a = '3';
  Object.prototype.a = '4';

  return function inner() {
    alert(foo.a);       // 3
    alert(bar.a);       // 4
    alert(new foo().a); // 2
    alert(new bar().a); // 1
  }
}

main()();

/* ================== */

/**
 *  Concepts:
 *    Execution Context
 */

(function () {

  alert(foo); // function pointer
  alert(bar); // undefined

  var foo = 'hello',
      bar = function () {
        return 'world';
      };

  function foo() {
    return 'hello';
  }

})()

/* ================== */

/*
 * Concepts:
 *   Lexical Scope
 */
var foo = 1;

function static() {
  alert(foo); // 1
}

!function () {
  var foo = 2;
  static();
}();

/* ================== */

/*
 * Concepts:
 *   Bind function
 */
this.x = 9;
var module = {
  x: 81,
  getX: function () {
    return this.x;
  }
};

var getX = module.getX;
getX(); // 9

var boundGetX = getX.bind(module);
boundGetX(); // 81

/* ================== */

/**
 * Concepts:
 *   Eval function
 */
var foo = 10;
(function (x) {
  var eval = x;
  var foo = 20;
  return [x('foo'), eval('foo')]
})(eval)

/* ================== */

/**
 * Concepts:
 *   If ... else ...
 * 
 * Reference:
 *   http://javascript.ruanyifeng.com/grammar/basic.html
 */

var m = 1;
var n = 2;

if (m !== 1) 
if (n === 2) console.log('hello'); 
else console.log('world');


/* ---------------
 * References:
 * 1. http://davidshariff.com/blog/what-is-the-execution-context-in-javascript/
 * 2. http://davidshariff.com/blog/javascript-scope-chain-and-closures/
 * 3. http://wingolog.org/archives/2012/01/12/javascript-eval-considered-crazy
 * 4. http://www.zhihu.com/question/20032419
 * 5. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind
 */