5 small examples that can help you understand JavaScript core closures and scope_javascript skills

Here are 5 small scripts that will help you truly understand the core of JavaScript – closures and scope. Before running the console, try answering what will pop up in each case. Then you can create a test file to check your answers. Are you ready?

1,

Copy code The code is as follows:

if (!("a" in window)) {
var a = 1;
}
alert(a);

2.

Copy code The code is as follows:

var a = 1,
b = function a(x) {
          x && a(--x);
};
alert(a);

3.

Copy code The code is as follows:

function a(x) {
Return x * 2;
}
var a;
alert(a);

4.

Copy code The code is as follows:

function b(x, y, a) {
arguments[2] = 10;
alert(a);
}
b(1, 2, 3);

5.

Copy code The code is as follows:

function a() {
alert(this);
}
a.call(null);

My predicted answers are: undefined, 1, don’t know, 10, null

The answer is at the end of this article. Before reading the answer, do you dare to leave your guess?

Correct answer: 1. undefined 2. 1 3. function a(x){ return x * 2} 4. 10 5. [object window]