JavaScript setter and getter methods

I have never used Javascript's setter and getter methods before when writing projects, so it is a concept that needs to be understood. Today I saw this knowledge point in a book, but it was still vague, so I planned to Research and study;

The properties of a Javascript object are composed of a name, a value and a set of properties. So first, let’s take a look at the two properties of the object:

Data properties, which we often use, should be familiar with
Accessor properties, also called accessor properties

What are accessor properties? It is a set of functions that get and set values. In ECMAScript5, property values ​​can be set using one or two methods, the two methods are getters and setters; therefore, properties defined by getters and setters are called accessor properties.

var o = {
  get val(){
    /*函数体*/
    return ;
  },
  set val(n){
    /*函数体*/
  }
}

The above is the simplest way to define an accessor property. It can be seen that the getter and setter methods actually replace A function of function.

var o = {
  a:3,
  get val(){
    return Math.pow(this.a,2);
  }
}

console.log(o.val);//9
o.val = 100;
console.log(o.val);//9

The getter method has no parameters and returns a value; when the getter method is set separately, only the attribute value can be obtained. The defined attribute values ​​cannot be changed, ensuring data security;

var o = {
  a:3,
  set val(n){
    this.a = n;
  }
}

console.log(o.val);//undefined

The setter method has parameters and no return value ; When setting the setter method alone, the attribute value cannot be read;

var o ={
  a:3,
  get val(){
    return Math.pow(this.a,n);
  },
  set val(n){
    this.a = Math.max(this.a,n);
  }
}

console.log(o.a);//3
console.log(o.val);//9
o.val = 10;
console.log(o.a);//10
console.log(o.val);//100

As can be seen from the above code, Where this refers to its object (i.e. "o" in the code);

var o ={
   a:3,
  get val(){
    return Math.pow(this.a,n);
  },
  set val(n){
    this.a = Math.max(this.a,n);
  }
}

o.val = 10;
var foo = Object.create(o);
console.log(foo.val);//10
foo.val = 9;
console.log(foo.val);//10

In addition, the accessor attribute can also be inherited.

Related recommendations:

Basic introduction to getters and setters in Javascript

##Sample code sharing of getter/setter implementation in JavaScript

Implemented the code of a PHP5 getter/setter base class_php skills

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