What is the use of js closure? Usage examples of js closure (with code)

This article brings you what is the use of js closure? The usage examples of js closure (with code) have certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Js language can directly read global variables inside the function, but local variables within the function cannot be read outside the function

Note: Be sure to add var when declaring variables inside the function , otherwise a global variable is declared.

function parent(){

m=50;

}

parent();

alert(m);//50

Sometimes, if you need to get the local variables inside the function, you need to use a flexible method to take advantage of the characteristics of js variable scope, such as defining a sub-function inside the function. For the sub-function, the parent function is it Globally, child functions can access variables in the parent function (which are local variables for the entire js code)

All local variables inside Parent are visible to its child functions, but its children Local variables within a function are invisible to its parent function. This is the unique chain scope structure of js. The child object will search for all the variables of the parent object level by level. All the variables of the parent object are All sub-objects are visible, but the reverse is not true! The son function above is a closure.

Closure: Define the function inside the function, the bridge connecting the inside and outside of the function. The closure has two functions:

• One is The variables inside the reading function mentioned earlier,

• The second is to save the values ​​​​of these variables in memory to achieve data sharing

The following are several examples of closures

1. Anonymous functions implement closures: