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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

Boolean() new Boolean() constructor prototype toString() valueOf()

constructor() extends static super

JS Dates JS Error

isError() name message

decodeURI() decodeURIComponent() encodeURI() encodeURIComponent() escape() eval() Infinity isFinite() isNaN() NaN Number() parseFloat() parseInt() String() undefined unescape()

drop() every() filter() find() flatMap() forEach() map() reduce() some() take()

parse() stringify()

new Map clear() delete() entries() forEach() get() groupBy() has() keys() set() size values()

JS Math JS Numbers JS Objects JS Operators JS Assignment

Assign Simple Assign Add Assign Subtract Assign Multiply Assign Divide Assign Remainder Assign Colon Assign AND Assign OR Assign Nullish

Addition Subtraction Multiplication Division Exponentiation Remainder Increment Decrement Concatenation Unary Plus Unary Negation

Equal Strict Equal Not Equal Strict Not Equal Greater Than Less Than Greater Equal Less Equal

JS Logical Operators

Logical AND Logical OR Logical NOT Logical Nullish

JS Bitwise Operators

Bitwise AND Bitwise OR Bitwise NOT Bitwise XOR Bitwise Left Bitwise Right Bitwise Signed

JS Misc Operators

: ?. ... () ? x : y => delete in instanceof typeof void

JS Precedence JS Promises

all() allSettled() any() catch() finally() race() reject() resolve() then()

JS RegExp Patterns

/d /g /i /m /s /u /v /y [a] [^a] [abc] [^abc] [A-Z] [^A-Z] [0-9] [^0-9] a|b . \w \W \d \D \s \S [\b] \0 \n \f \r \t \v \p \P \ddd \xhh \uhhhh ^ $ \b \B x(?=y) x(?!y) (?<=y)x (?<!y)x (x) (?<name>x) (?flags:x) + * ? {n} {n,m} {n,}

JS RegExp Reference

compile() constructor dotAll escape() exec() flags global hasIndices ignoreCase lastIndex multiline source sticky test() toString() unicode unicodeSets

new Set add() clear() delete() difference() entries() forEach() has() intersection() isDisjointFrom() isSubsetOf() isSupersetOf() keys() size symmetricDifference() union() values()

break class const continue debugger do...while for for...in for...of function if...else let return switch throw try...catch var while

JS Strings JS Typed Arrays

Int8Array Uint8Array Uint8ClampedArray Int16Array Uint16Array Int32Array Uint32Array BigInt64Array BigUint64Array Float16Array Float32Array Float64Array

JS Typed Reference

Window

Window Object Window Console

assert() clear() count() error() group() groupCollapsed() groupEnd() info() log() table() time() timeEnd() trace() warn()

back() forward() go() length

Window Location

assign() hash host hostname href origin pathname port protocol reload() replace() search

Window Navigator

appCodeName appName appVersion cookieEnabled geolocation javaEnabled() language onLine platform product taintEnabled() userAgent

availHeight availWidth colorDepth height pixelDepth width

HTML DOM

HTML Documents HTML Elements

accessKey addEventListener() after() append() appendChild() attributes before() blur() childElementCount childNodes children classList className click() clientHeight clientLeft clientTop clientWidth cloneNode() closest() compareDocumentPosition() contains() contentEditable dir firstChild firstElementChild focus() getAttribute() getAttributeNode() getBoundingClientRect() getElementsByClassName() getElementsByTagName() hasAttribute() hasAttributes() hasChildNodes() id innerHTML innerText insertAdjacentElement() insertAdjacentHTML() insertAdjacentText() insertBefore() isContentEditable isDefaultNamespace() isEqualNode() isSameNode() isSupported() lang lastChild lastElementChild matches() namespaceURI nextSibling nextElementSibling nodeName nodeType nodeValue normalize() offsetHeight offsetWidth offsetLeft offsetParent offsetTop outerHTML outerText ownerDocument parentNode parentElement previousSibling previousElementSibling querySelector() querySelectorAll() remove() removeAttribute() removeAttributeNode() removeChild() removeEventListener() replaceChild() scrollHeight scrollIntoView() scrollLeft scrollTop scrollWidth setAttribute() setAttributeNode() style tabIndex tagName textContent title

HTML Attributes

getNamedItem() isId item() length name removeNamedItem() setNamedItem() specified value

HTML Collection

item() length namedItem()

entries() forEach() item() keys() length values()

HTML DOMTokenList

add() contains() entries() forEach() item() keys() length remove() replace() supports() toggle() value values()

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

Animation Events Clipboard Events Drag Events Events Focus Events HashChange Events Input Events Keyboard Events Mouse Events PageTransition Events PopState Events Progress Events Storage Events Touch Events Transition Events Ui Events Wheel Events

HTML Event Properties HTML Event Methods

getModifierState() preventDefault() stopImmidiatePropagation() stopPropagation()

Web APIs

API Canvas API Console API Fetch API Fullscreen

exitFullscreen() fullscreenElement fullscreenEnabled() requestFullscreen()

API Geolocation

coordinates getCurrentPosition() position

API History API MediaQueryList API Storage

clear() getItem() key() length removeItem() setItem()

API Validation API Web

crypto.getRandomNumber()

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

cssText getPropertyPriority() getPropertyValue() item() length parentRule removeProperty() setProperty()

JS 类型转换

Option defaultSelected 属性

❮ Option 对象

实例

检查选中的选项是否默认选中:

var x = document.getElementById("mySelect").selectedIndex;
var y = document.getElementsByTagName("option");
alert("Is " + y[x].text + " selected by default? " + y[x].defaultSelected);

亲自试一试 »

定义和用法

defaultSelected 属性返回所选属性的默认值。

如果默认选择了一个选项，该属性返回true，否则返回false。

注释:如果一个选项默认被选中，它首先显示在下拉列表中。

浏览器支持

属性
defaultSelected	Yes	Yes	Yes	Yes	Yes

语法

optionObject.defaultSelected

技术细节

返回值:	一个布尔值，如果默认选择该选项返回true，否则返回false

❮ Option 对象

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