How Does the `this` Keyword Behave in JavaScript Object Literals?
Dec 13, 2024 pm 09:48 PM"this" Keyword Behavior in Javascript Object Literals
Within an object literal, the "this" keyword serves as a placeholder for the object itself. However, its behavior can vary depending on the condition in which it is called.
In your code:
var MyDate = function(date) { this.date = date; }; var obj1 = { foo: new Date(), bar: new MyDate(this.foo) // this.foo is undefined }; var obj2 = {}; obj2.foo = new Date(); obj2.bar = new MyDate(this.foo); // this.foo is undefined var obj3 = { foo: new Date(), bar: new MyDate(obj3.foo) }; var obj4 = {}; obj4.foo = new Date(); obj4.bar = new MyDate(obj4.foo);
Understanding "this" Binding
Javascript's "this" keyword exhibits late binding, meaning its value is not determined until the function is invoked. In your case:
Scenario 1 and 2:
- In "obj1" and "obj2," the "this" keyword within the "new MyDate" function refers to the global object (i.e., "window") because they are not invoked as methods of a specific object. Since there's no property named "foo" on the global object, it results in an undefined error.
Scenario 3 and 4:
- In "obj3" and "obj4," the "this" keyword successfully refers to the respective objects because the "new MyDate" function is called as a method of these objects. Therefore, "this.foo" correctly accesses the "foo" property within each object.
Conclusion
The behavior of the "this" keyword within object literals depends on the context in which the function is invoked. If not explicitly bound to an object, it defaults to the global object. However, when called as a method of an object, it refers to that specific object, ensuring proper access to the object's properties and methods.
The above is the detailed content of How Does the `this` Keyword Behave in JavaScript Object Literals?. For more information, please follow other related articles on the PHP Chinese website!

Hot Article

Hot tools Tags

Hot Article

Hot Article Tags

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

Replace String Characters in JavaScript

Custom Google Search API Setup Tutorial

8 Stunning jQuery Page Layout Plugins

Improve Your jQuery Knowledge with the Source Viewer

10 Mobile Cheat Sheets for Mobile Development
