The process of new an object in js

This article mainly introduces the process of new object in js. It has a very good reference value. Let’s take a look at it with the editor.

The specific steps of using the new keyword to call the function (new ClassA(...)):

1. Create an empty object {}

2. Use the new object and call the function. This in the function is pointed to the new instance object :

                                                                                                                                                                                        Constructor();                                                       The constructor attribute is the name of the constructor. Set the __proto__ attribute of the new object to point to the prototype object of the constructor

4. Set the address of the new object that has been initialized , saved to the variable on the left side of the equal sign

Note: If there is no return value in the constructor or the return value is of a basic type (Number, String, Boolean) value, a new instance object is returned; if the return value is a reference type value, the actual return value is this reference type.

var foo = "bar";
function test () {
 this.foo = "foo";
}
new test();  　　　　　　　　//test中的this指新对象，并未改变全局的foo属性
console.log(this.foo);  // "bar"
console.log(new testThis().foo); // "foo";new和属性访问.运算符优先级相通，从左往右执行

The above is my personal understanding. If there are any errors, please leave a message to correct me.

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