for 语句用于创建一个循环,它包含了三个可选的表达式,这三个表达式被包围在圆括号之中,使用分号分隔,后跟一个用于在循环中执行的语句(通常是一个块语句)。
Learn more See full compatibility Report feedback 与其他语言相比,函数的 this 关键字在JavaScript 中的表现略有不同,此外,在严格模式和非严格模式之间也会有一些差别。 在绝大多数情况下,函数的调用方式决定了 this 的值(运行时绑定)。this 不能在执行期间被赋值,并且在每次函数被调用时 this 的值也可能会不...
1.0Toggle history 4.0.0Toggle history Legend Tip: you can click/tap on a cell for more information. Full support Full support Partial support Partial support No support No support Non-standard. Check cross-browser support before using. See implementation notes. Has more compatibility info. ...
In JavaScript, everything is an object. An object is a collection of related functionality stored in a single grouping. You can create your own objects, but that is quite advanced. The built-in objects that your browser contains allow you to do lots of useful things. For example, we first...
Specifications Specification DOM Standard #interface-document HTML Standard #the-document-object CSSOM View Module #extensions-to-the-document-interface Pointer Lock 2.0 #extensions-to-the-document-interface Selection API #extensions-to-document-interface...
1 Toggle history 8 Toggle history 1 Toggle history 18 Toggle history 4 Toggle history 10.1 Toggle history 1 Toggle history 1.0 Toggle history 1 Toggle history Legend Tip: you can click/tap on a cell for more information. Full support
If you want to take control over the look and feel of native error messages, or if you want to deal with browsers that do not support HTML's built-in form validation, you must use JavaScript. More and more browsers now support the constraint validation API, and it's becoming reliable. ...
This document covers topics that a professional writer who will be working full-time on MDN needs to know to get started. If you contribute to MDN on a casual basis, you don't need to worry about this; you can just dive in andget started. Or you can peruse these topics at your leis...
To take full advantage of these technologies, you need to know how to use them. Below you’ll find links to our Web technology documentation. 所有教程概述 For complete beginners to the Web HTML Tutorials
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015. Learn more See full compatibility Report feedback for...in 语句迭代一个对象的所有可枚举字符串属性(除 Symbol 以外),包括继承的可枚举属性。