You think you know a lot about javascript?

(Please understand the improper translation)

Source: http://www.ido321.com/914.html

Here are 5 small scripts that will help you really understand the JavaScript core – closures and scopes. Before the console executes, try to answer what pops up in each case, and then you can create a test file to check your answers.

Are you ready?

1.

   1:if (! ( "a"  in window) {

   2:     var a = 1;

   3:  }

   4:  alert (a);

2.

   1:var a = 1,

   2:     function A (x) {

   3:         x && A (--x);

   4:     };

   5:  alert (a);

3.

   1:function A (x) {

   2:     return x * 2;

   3:  }

   4:var A;

   5:  alert (a);

4.

   1:function b (x, Y, a) {

   2:     arguments[2] = ten;

   3:     alert (a);

   4:  }

   5:  B (1, 2, 3);

5.

   1:function A () {

   2:     alert (this);

   3:  }

   4:  a.call (null);

My pre-Test answers are: Undefined, 1, not known, 10, null

At the end of this article, do you dare to leave your test before reading the answer?

Correct answers: 1, undefined 2, 1 3, function A (x) {return x * 2} 4, 10 5, [object window]

Source: http://dmitry.baranovskiy.com/post/91403200

You think you know a lot about javascript?