One JavaScript instance every day-use a function closure with a timer and a javascript Timer

One JavaScript instance every day-use a function closure with a timer and a javascript Timer

<! DOCTYPE html> 



What is the function of the javascript closure? Let's take an example to illustrate it. Thank you!
Simple concepts of closures:
A closure is a function that can read internal variables of other functions.
The two largest functions of function closures inside a function
Read the internal variables of the function.
The variable value is always in the memory.
Function ()
{
Var n = 999;
NAdd = function () {n + = 1}
Function B ()
{

Alert (n );

}
Return B;
}
Var result = ();
Result (); // 999.
NAdd ();
Result (); // 1000.

Javascript closures and variables
Return function (){
Return num;
};

This method is accessible.

Function (num) {'''} (I );
Remember this.