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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 Array
concat() constructor copyWithin() entries() every() fill() filter() find() findIndex() forEach() from() includes() indexOf() isArray() join() keys() length lastIndexOf() map() pop() prototype push() reduce() reduceRight() reverse() shift() slice() some() sort() splice() toString() unshift() valueOf()
JS Boolean
constructor prototype toString() valueOf()
JS Classes
constructor() extends static super
JS Date
constructor getDate() getDay() getFullYear() getHours() getMilliseconds() getMinutes() getMonth() getSeconds() getTime() getTimezoneOffset() getUTCDate() getUTCDay() getUTCFullYear() getUTCHours() getUTCMilliseconds() getUTCMinutes() getUTCMonth() getUTCSeconds() now() parse() prototype setDate() setFullYear() setHours() setMilliseconds() setMinutes() setMonth() setSeconds() setTime() setUTCDate() setUTCFullYear() setUTCHours() setUTCMilliseconds() setUTCMinutes() setUTCMonth() setUTCSeconds() toDateString() toISOString() toJSON() toLocaleDateString() toLocaleTimeString() toLocaleString() toString() toTimeString() toUTCString() UTC() valueOf()
JS Error
name message
JS Global
decodeURI() decodeURIComponent() encodeURI() encodeURIComponent() escape() eval() Infinity isFinite() isNaN() NaN Number() parseFloat() parseInt() String() undefined unescape()
JS JSON
parse() stringify()
JS Math
abs() acos() acosh() asin() asinh() atan() atan2() atanh() cbrt() ceil() clz32() cos() cosh() E exp() expm1() floor() fround() LN2 LN10 log() log10() log1p() log2() LOG2E LOG10E max() min() PI pow() random() round() sign() sin() sqrt() SQRT1_2 SQRT2 tan() tanh() trunc()
JS Number
constructor isFinite() isInteger() isNaN() isSafeInteger() MAX_VALUE MIN_VALUE NEGATIVE_INFINITY NaN POSITIVE_INFINITY prototype toExponential() toFixed() toLocaleString() toPrecision() toString() valueOf()
JS 运算符 JS RegExp
constructor compile() exec() g global i ignoreCase lastIndex m multiline n+ n* n? n{X} n{X,Y} n{X,} n$ ^n ?=n ?!n source test() toString() [abc] [^abc] [0-9] [^0-9] (x|y) . \w \W \d \D \s \S \b \B \0 \n \f \r \t \v \xxx \xdd \uxxxx
JS 语句
break class continue debugger do...while for for...in for...of function if...else return switch throw try...catch var while
JS String
charAt() charCodeAt() concat() constructor endsWith() fromCharCode() includes() indexOf() lastIndexOf() length localeCompare() match() prototype repeat() replace() search() slice() split() startsWith() substr() substring() toLocaleLowerCase() toLocaleUpperCase() toLowerCase() toString() toUpperCase() trim() valueOf()

HTML DOM

DOM Attributes
getNamedItem() isId item() length name removeNamedItem() setNamedItem() specified value
DOM Document
activeElement addEventListener() adoptNode() anchors applets baseURI body close() cookie charset characterSet createAttribute() createComment() createDocumentFragment() createElement() createEvent() createTextNode() defaultView designMode doctype documentElement documentMode documentURI domain embeds execCommand() forms fullscreenElement fullscreenEnabled() getElementById() getElementsByClassName() getElementsByName() getElementsByTagName() hasFocus() head images implementation importNode() inputEncoding lastModified links normalize() normalizeDocument() open() querySelector() querySelectorAll() readyState referrer removeEventListener() renameNode() scripts strictErrorChecking title URL write() writeln()
DOM Element
accessKey addEventListener() appendChild() attributes blur() childElementCount childNodes children classList className click() clientHeight clientLeft clientTop clientWidth cloneNode() closest() compareDocumentPosition() contains() contentEditable dir exitFullscreen() 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() requestFullscreen() scrollHeight scrollIntoView() scrollLeft scrollTop scrollWidth setAttribute() setAttributeNode() style tabIndex tagName textContent title
DOM Events
abort afterprint animationend animationiteration animationstart beforeprint beforeunload blur canplay canplaythrough change click contextmenu copy cut dblclick drag dragend dragenter dragleave dragover dragstart drop durationchange ended error focus focusin focusout fullscreenchange fullscreenerror hashchange input invalid keydown keypress keyup load loadeddata loadedmetadata loadstart message mousedown mouseenter mouseleave mousemove mouseover mouseout mouseup offline online open pagehide pageshow paste pause play playing progress ratechange resize reset scroll search seeked seeking select show stalled submit suspend timeupdate toggle touchcancel touchend touchmove touchstart transitionend unload volumechange waiting wheel altKey altKey animationName bubbles button buttons cancelable charCode clientX clientY code createEvent() ctrlKey ctrlKey currentTarget data defaultPrevented deltaX deltaY deltaZ deltaMode detail elapsedTime elapsedTime eventPhase getModifierState() inputType isTrusted key keyCode location metaKey metaKey newURL oldURL pageX pageY persisted preventDefault() propertyName relatedTarget relatedTarget screenX screenY shiftKey shiftKey stopImmediatePropagation() stopPropagation() target targetTouches timeStamp touches type which which view
DOM Event 对象
AnimationEvent ClipboardEvent DragEvent Event FocusEvent HashChangeEvent InputEvent KeyboardEvent MouseEvent PageTransitionEvent PopStateEvent ProgressEvent StorageEvent TouchEvent TransitionEvent UiEvent WheelEvent
DOM HTMLCollection
item() length namedItem()
DOM Location
hash host hostname href origin pathname port protocol search assign() reload() replace()
DOM Navigator
appCodeName appName appVersion cookieEnabled geolocation language onLine platform product userAgent javaEnabled() taintEnabled()
DOM Screen
availHeight availWidth colorDepth height pixelDepth width
DOM Style
alignContent alignItems alignSelf animation animationDelay animationDirection animationDuration animationFillMode animationIterationCount animationName animationTimingFunction animationPlayState background backgroundAttachment backgroundColor backgroundImage backgroundPosition backgroundRepeat backgroundClip backgroundOrigin 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 cursor direction display emptyCells filter flex flexBasis flexDirection flexFlow flexGrow flexShrink flexWrap cssFloat 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
DOM Window
closed console defaultStatus document frameElement frames history innerHeight innerWidth length localStorage location name navigator opener outerHeight outerWidth pageXOffset pageYOffset parent screen screenLeft screenTop screenX screenY sessionStorage self status top alert() atob() blur() btoa() clearInterval() clearTimeout() close() confirm() focus() getComputedStyle() matchMedia() moveBy() moveTo() open() print() prompt() resizeBy() resizeTo() scrollBy() scrollTo() setInterval() setTimeout() stop()

Web APIs

API Console
assert() clear() count() error() group() groupCollapsed() groupEnd() info() log() table() time() timeEnd() trace() warn()
API Geolocation
coordinates position
API History
back() forward() go() length
API Storage
key() length getItem() setItem() removeItem() clear()

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


Video poster 属性

❮ Video 对象

实例

更改视频的海报图片：

document.getElementById("myVideo").poster = "/images/w3schoolscomlogo.png";
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定义和用法

poster 属性设置或返回视频的poster属性的值。

poster 属性指定在视频下载时或用户点击播放按钮之前要显示的图像。 如果这不包括在内，则将使用视频的第一帧。

浏览器支持

Property
poster Yes 9.0 Yes Yes Yes

语法

返回 poster 属性:

videoObject.poster

设置 poster 属性:

videoObject.poster = URL

属性值

值 描述
URL 指定图像文件的 URL。

可能的值：

  • 绝对 URL - 指向另一个网站（例如 href="http://www.example.com/poster.jpg"）
  • 相对 URL - 指向网站内的文件（如 href="poster.jpg"）

技术细节

返回值: 字符串，代表海报图片的URL。 返回整个 URL，包括协议（如 http://）

更多实例

实例

获取海报图片的网址：

var x = document.getElementById("myVideo").poster;
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相关页面

HTML 参考手册: HTML <video> poster 属性

❮ Video 对象