The role of this in js

In JavaScript, this is a special keyword that points to the context object of the currently executing code: Function context: this points to the global object window. Method context: this points to the object on which the method is called. Constructor context: this points to the new object being created. Event listener context: this points to the element that triggered the event. Arrow function context: this inherits this from the parent scope.

this in JavaScript

In JavaScript, this is a special keyword that points to the context object of the currently executing code. Its value varies depending on the context because it can refer to a function, method, or object.

Function context

In a function context, this always points to the global object, that is, the window object. Therefore, when accessing this within a function, global variables and functions can be accessed.

function sayHello() {
  console.log(this); // 输出: Window {...}
}

Method context

In a method context, this always points to the object on which the method is called. This allows methods to access the object's properties and methods.

const person = {
  name: "John",
  sayName: function () {
    console.log(this.name); // 输出: John
  },
};

Constructor context

The constructor is a function used to create and initialize objects. In constructor context, this points to the new object being created.

function Person(name) {
  this.name = name;
}

const person1 = new Person("John");
console.log(person1.name); // 输出: John

Other contexts

In addition to these primary contexts, this can also be used as:

• Event listener context: In an event listener, this points to the element that triggered the event.
• Arrow function context: this in an arrow function inherits this in its parent scope.

Notes

• In strict mode, in the function context, this does not point to the global object. If you want to access global objects, you need to use the window object.
• The bind(), call() and apply() methods were introduced in ES6 for explicitly setting or changing ## The value of #this.

The above is the detailed content of The role of this in js. For more information, please follow other related articles on the PHP Chinese website!