Easily learn Javascript closure functions_javascript tips

What is a closure function?When you first start learning closures, it is probably difficult for everyone to understand. Judging from its official explanation, it is relatively conceptual.

But we still start from the meaning of closure.
Closure means that a function has free and independent variables. In other words, a function defined in a closure can "remember" the environment in which it was created.
After the official explanation, let’s first look at a simple counting example.

var c = 0;
function count(){
c++;
}
count();// 1
count();// 2

This example is implemented using global variables, but there is a problem here. The variable c is also easily called by other methods. At this time, the stored value of c may be changed, causing the count to become invalid. Then How to deal with this problem well! What we will think of is to use local variables to deal with it. For example:

function count(){
 var c = 0;
 function add(){
  c++;
 }
 add();
}
count();// c = 1
count();// c = 1

Because after creation in this way, the internal variables only exist when the count function is created and executed. After execution, the entire function will be discarded. The ability to have memory cannot be achieved. So how to achieve it? Then we will Use closures to solve it. I want to mention it again: closure = function + environment

function count(){
  var c = 0;
  function add(){
   c++;
  }
  return add;
}
var ct = count();
ct(); // c = 1
ct(); // c = 2

At this time, we can use this closure to complete the counting ability. ct is a closure function, and the internal environment is the local variable c. What we achieve here is the internal data, which is operated externally. In addition to the closure What other functions does this have?

Use closures to simulate private methods
This is a bit like JAVA's private methods or private variables, which can only be operated by yourself! If you operate externally, you need to set a public method to operate.

var person = (function(){
  var _name = "编程的人";
  var age = 20;
  return {
   add:function(){
     age++;
   },
   jian:function(){
     age--;
   },
   getAge:function() {
     return age;
   },
   getName:function(){
     return _name;
   },
   setName: function (name) {
     _name = name;        
   }
  }
})();
person.add();
var age = person.getAge();
console.log(age)
person.setName("编程的人公众号:bianchengderen")
console.log(person.getName())

It should be easy to understand here! It feels a bit like object-oriented programming. Of course, Javascript now also has the characteristics of object-oriented programming. We will explain this later.
So far, we have used examples from counting to internal privatization to illustrate closures. I hope everyone can easily understand the principle. Of course, closures have other functions that are more convenient to use.

The above is the entire content of this article. I hope it will be helpful to everyone in learning javascript programming.