JS 参考手册

JS 参考手册(类别排序) JS 参考手册(字母排序)

JavaScript

JS Arrays JS Boolean JS Classes JS Dates JS Error JS Global JS Iterators JS JSON JS Maps JS Math JS Numbers JS Objects JS Operators JS Assignment JS Arithmetic JS Comparison JS Logical Operators JS Bitwise Operators JS Misc Operators JS Precedence JS Promises JS RegExp Patterns JS RegExp Reference JS Sets JS Statements JS Strings JS Typed Arrays JS Typed Reference

Window

Window Object Window Console Window History Window Location Window Navigator Window Screen

HTML DOM

HTML Documents HTML Elements HTML Attributes HTML Collection HTML NodeList HTML DOMTokenList HTML Styles
alignContent alignItems alignSelf animation animationDelay animationDirection animationDuration animationFillMode animationIterationCount animationName animationTimingFunction animationPlayState background backgroundAttachment backgroundClip backgroundColor backgroundImage backgroundOrigin backgroundPosition backgroundRepeat backgroundSize backfaceVisibility border borderBottom borderBottomColor borderBottomLeftRadius borderBottomRightRadius borderBottomStyle borderBottomWidth borderCollapse borderColor borderImage borderImageOutset borderImageRepeat borderImageSlice borderImageSource borderImageWidth borderLeft borderLeftColor borderLeftStyle borderLeftWidth borderRadius borderRight borderRightColor borderRightStyle borderRightWidth borderSpacing borderStyle borderTop borderTopColor borderTopLeftRadius borderTopRightRadius borderTopStyle borderTopWidth borderWidth bottom boxShadow boxSizing captionSide caretColor clear clip color columnCount columnFill columnGap columnRule columnRuleColor columnRuleStyle columnRuleWidth columns columnSpan columnWidth counterIncrement counterReset cssFloat cursor direction display emptyCells filter flex flexBasis flexDirection flexFlow flexGrow flexShrink flexWrap font fontFamily fontSize fontStyle fontVariant fontWeight fontSizeAdjust height isolation justifyContent left letterSpacing lineHeight listStyle listStyleImage listStylePosition listStyleType margin marginBottom marginLeft marginRight marginTop maxHeight maxWidth minHeight minWidth objectFit objectPosition opacity order orphans outline outlineColor outlineOffset outlineStyle outlineWidth overflow overflowX overflowY padding paddingBottom paddingLeft paddingRight paddingTop pageBreakAfter pageBreakBefore pageBreakInside perspective perspectiveOrigin position quotes resize right scrollBehavior tableLayout tabSize textAlign textAlignLast textDecoration textDecorationColor textDecorationLine textDecorationStyle textIndent textOverflow textShadow textTransform top transform transformOrigin transformStyle transition transitionProperty transitionDuration transitionTimingFunction transitionDelay unicodeBidi userSelect verticalAlign visibility width wordBreak wordSpacing wordWrap widows zIndex

HTML Events

HTML Events HTML Event Objects HTML Event Properties HTML Event Methods

Web APIs

API Canvas API Console API Fetch API Fullscreen API Geolocation API History API MediaQueryList API Storage API Validation API Web

HTML 对象

<a> <abbr> <address> <area> <article> <aside> <audio> <b> <base> <bdo> <blockquote> <body> <br> <button> <canvas> <caption> <cite> <code> <col> <colgroup> <datalist> <dd> <del> <details> <dfn> <dialog> <div> <dl> <dt> <em> <embed> <fieldset> <figcaption> <figure> <footer> <form> <head> <header> <h1> - <h6> <hr> <html> <i> <iframe> <img> <ins> <input> button <input> checkbox <input> color <input> date <input> datetime <input> datetime-local <input> email <input> file <input> hidden <input> image <input> month <input> number <input> password <input> radio <input> range <input> reset <input> search <input> submit <input> text <input> time <input> url <input> week <kbd> <label> <legend> <li> <link> <map> <mark> <menu> <menuitem> <meta> <meter> <nav> <object> <ol> <optgroup> <option> <output> <p> <param> <pre> <progress> <q> <s> <samp> <script> <section> <select> <small> <source> <span> <strong> <style> <sub> <summary> <sup> <table> <tbody> <td> <tfoot> <th> <thead> <tr> <textarea> <time> <title> <track> <u> <ul> <var> <video>

其他参考手册

CSSStyleDeclaration JS 类型转换


Script async 属性

❮ Script 对象

实例

找出脚本是否在可用时立即异步执行:

var x = document.getElementById("myScript").async
亲自试一试 »

定义和用法

async 属性设置或返回脚本是否应在可用时立即异步执行。

该属性反映了 <script> 标签的 async 属性。

注释: async 属性仅适用于外部脚本(并且仅应在存在 src 属性时使用)。

注释:可以通过多种方式执行外部脚本:

  • 如果存在异步:脚本与页面的其余部分异步执行(脚本将在页面继续解析时执行)
  • 如果 async 不存在且 defer 存在:脚本在页面完成解析后执行
  • 如果 async 或 defer 都不存在:在浏览器继续解析页面之前立即获取并执行脚本

浏览器支持

表中的数字表示支持该属性的第一个浏览器版本。

属性
async Yes 10.0 Yes Yes Yes

语法

返回 async 属性:

scriptObject.async

设置 async 属性:

scriptObject.async = true|false

属性值

值 描述
true|false 指定脚本是否应在可用时立即异步执行,或者不
  • true - 脚本将在可用时立即异步执行
  • false - 脚本一旦可用就不会异步执行

技术细节

返回值: 一个布尔值,如果脚本一可用就异步执行,则返回true,否则返回false

相关页面

HTML 参考手册: HTML <script> async 属性


❮ Script 对象

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