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JavaScript鏁扮粍鎵€鏈堿PI鍏ㄨВ瀵?鍗氬-浜戞爾紺懼尯-闃塊噷浜?
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澹版槑锛氫互涓嬫湭鐗瑰埆鏍囨槑鐨勬柟娉曞潎涓篍S5宸插疄鐜扮殑鏂規硶銆?/p>
Array鏋勯€犲櫒
Array鏋勯€犲櫒鐢ㄤ簬鍒涘緩涓€涓柊鐨勬暟緇勩€傞€氬父锛屾垜浠帹鑽愪嬌鐢ㄥ璞″瓧闈㈤噺鍒涘緩鏁扮粍锛岃繖鏄竴涓ソ涔犳儻锛屼絾鏄€繪湁瀵矽薄瀛楅潰閲忎箯鍔涚殑鏃跺€欙紝姣斿璿達紝鎴戞兂鍒涘緩涓€涓暱搴︿負8鐨勭┖鏁扮粍銆傝姣旇緝濡備笅涓ょ鏂瑰紡锛?/p>
// 浣跨敤Array鏋勯€犲櫒var a = Array(8); // [undefined 脳 8]
// 浣跨敤瀵矽薄瀛楅潰閲?/code>var b = [];
b.length = 8; // [undefined 脳 8]
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Array鏋勯€犲櫒鏄庢樉瑕佺畝媧佷竴浜涳紝褰撶劧浣犱篃璁鎬細璿達紝瀵矽薄瀛楅潰閲忎篃涓嶉敊鍟婏紝閭ｄ箞鎴戜繚鎸佹矇榛樸€?br >
濡備笂锛屾垜浣跨敤浜咥rray(8)鑰屼笉鏄痭ew Array(8)锛岃繖浼氭湁褰卞搷鍚楋紵瀹為檯涓婏紝騫舵病鏈夊獎鍝嶏紝榪欏緱鐩婁簬Array鏋勯€犲櫒鍐呴儴瀵箃his鎸囬拡鐨勫垽鏂紝ELS5_HTML瑙勮寖鏄繖涔堣鐨勶細
When Array is called as a function rather than as a constructor, it creates and initialises a new Array object. Thus the function call Array(鈥? is equivalent to the object creation expression new Array(鈥? with the same arguments.
浠庤鑼冩潵鐪嬶紝嫻忚鍣ㄥ唴閮ㄥぇ鑷村仛浜嗗涓嬬被浼肩殑瀹炵幇锛?/p>
function Array(){
聽聽// 濡傛灉this涓嶆槸Array鐨勫疄渚嬶紝閭ｅ氨閲嶆柊new涓€涓疄渚?/code>
聽聽if(!(this instanceof arguments.callee)){
聽聽聽聽return new arguments.callee();
聽聽}
} |
涓婇潰锛屾垜浼間箮璺寵繃浜嗗Array鏋勯€犲櫒璿硶鐨勪粙緇嶏紝娌′簨锛屾帴涓嬫潵鎴戣ˉ涓娿€?/p>
Array鏋勯€犲櫒鏍規嵁鍙傛暟闀垮害鐨勪笉鍚岋紝鏈夊涓嬩袱縐嶄笉鍚岀殑澶勭悊锛?/p>
- new Array(arg1, arg2,鈥?锛屽弬鏁伴暱搴︿負0鎴栭暱搴﹀ぇ浜庣瓑浜?鏃訛紝浼犲靉鐨勫弬鏁板皢鎸夌収欏哄簭渚濇鎴愪負鏂版暟緇勭殑絎?鑷砃欏癸紙鍙傛暟闀垮害涓?鏃訛紝榪斿洖絀烘暟緇勶級銆?/li>
- new Array(len)锛屽綋len涓嶆槸鏁板€兼椂锛屽鐞嗗悓涓婏紝榪斿洖涓€涓彧鍖呭惈len鍏冪礌涓€欏圭殑鏁扮粍锛涘綋len涓烘暟鍊兼椂锛屾牴鎹涓嬭鑼冿紝len鏈€澶т笉鑳借秴榪?2浣嶆棤絎﹀彿鏁村瀷锛屽嵆闇€瑕佸皬浜?鐨?2嬈℃柟锛坙en鏈€澶т負Math.pow(2,32) -1鎴?1>>>0锛夛紝鍚﹀墶灝嗘姏鍑篟angeError銆?/li>
If the argument len is a Number and ToUint32(len) is equal to len, then the length property of the newly constructed object is set to ToUint32(len). If the argument len is a Number and ToUint32(len) is not equal to len, a RangeError exception is thrown.
浠ヤ笂锛岃娉ㄦ剰Array鏋勯€犲櫒瀵逛簬鍗曚釜鏁板€煎弬鏁扮殑鐗規畩澶勭悊锛屽鏋滀粎浠呴渶瑕佷嬌鐢ㄦ暟緇勫寘瑁?? 鑻ュ共鍙傛暟锛屼笉濡ㄤ嬌鐢ˋrray.of锛屽叿浣撹縐繪涓嬩竴鑺傘€?/p>
濡傛灉浣犳兂瀛︿範鍓嶇鍙互鏉ヨ繖涓兢锛岄鍏堟槸浜屼節涓€锛屼腑闂存槸鍏簲涓€锛屾渶鍚庢槸涓€鍏節锛岄噷闈㈠彲浠ュ涔犱氦嫻侊紝涔熸湁璧勬枡鍙互涓嬭澆銆?/p>
ES6鏂板鐨勬瀯閫犲嚱鏁版柟娉?/h2>
閴翠簬鏁扮粍鐨勫父鐢ㄦ€э紝ES6涓撻棬鎵╁睍浜嗘暟緇勬瀯閫犲櫒Array 锛屾柊澧?涓柟娉曪細Array.of銆丄rray.from銆備笅闈㈠睍寮€鏉ヨ亰銆?/p>
Array.of
Array.of鐢ㄤ簬灝嗗弬鏁頒緷嬈¤漿鍖栦負鏁扮粍涓殑涓€欏癸紝鐒跺悗榪斿洖榪欎釜鏂版暟緇勶紝鑰屼笉綆¤繖涓弬鏁版槸鏁板瓧榪樻槸鍏跺畠銆傚畠鍩烘湰涓婁笌Array鏋勯€犲櫒鍔熻兘涓€鑷達紝鍞竴鐨勫尯鍒氨鍦ㄥ崟涓暟瀛楀弬鏁扮殑澶勭悊涓娿€傚涓嬶細
Array.of(8.0); // [8]
Array(8.0); // [undefined 脳 8]
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鍙傛暟涓哄涓紝鎴栧崟涓弬鏁頒笉鏄暟瀛楁椂锛孉rray.of 涓?Array鏋勯€犲櫒絳夊悓銆?/p>
Array.of(8.0, 5); // [8, 5]
Array(8.0, 5); // [8, 5]
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Array.of('8'); // ["8"]
Array('8'); // ["8"]
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鍥犳锛岃嫢鏄渶瑕佷嬌鐢ㄦ暟緇勫寘瑁瑰厓緔狅紝鎺ㄨ崘浼樺厛浣跨敤Array.of鏂規硶銆?/p>
鐩墠锛屼互涓嬬増鏈祻瑙堝櫒鎻愪緵浜嗗Array.of鐨勬敮鎸併€?/p>
| Chrome | Firefox | Edge | Safari |
|---|---|---|---|
| 45+ | 25+ | 9.0+ |
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if (!Array.of){
聽聽Array.of = function(){
聽聽聽聽return Array.prototype.slice.call(arguments);
聽聽};
} |
Array.from
璿硶锛欰rray.from(arrayLike[, processingFn[, thisArg]])
Array.from鐨勮璁″垵琛鋒槸蹇€熶究鎹風殑鍩轟簬鍏朵粬瀵矽薄鍒涘緩鏂版暟緇勶紝鍑嗙‘鏉ヨ灝辨槸浠庝竴涓被浼兼暟緇勭殑鍙凱浠ｅ璞″壋寤轟竴涓柊鐨勬暟緇勫疄渚嬶紝璿翠漢璿濆氨鏄紝鍙涓€涓璞℃湁榪唬鍣紝Array.from灝辮兘鎶婂畠鍙樻垚涓€涓暟緇勶紙褰撶劧锛屾槸榪斿洖鏂扮殑鏁扮粍锛屼笉鏀瑰彉鍘熷璞★級銆?/p>
浠庤娉曚笂鐪嬶紝Array.from鎷ユ湁3涓艦鍙傦紝絎竴涓負綾諱技鏁扮粍鐨勫璞★紝蹇呴€夈€傜浜屼釜涓哄姞宸ュ嚱鏁幫紝鏂扮敓鎴愮殑鏁扮粍浼氱粡榪囪鍑芥暟鐨勫姞宸ュ啀榪斿洖銆傜涓変釜涓簍his浣滅敤鍩燂紝琛ㄧず鍔犲伐鍑芥暟鎵ц鏃秚his鐨勫€箋€傚悗涓や釜鍙傛暟閮芥槸鍙€夌殑銆傛垜浠潵鐪嬬湅鐢ㄦ硶銆?/p>
var obj = {0: 'a', 1: 'b', 2:'c', length: 3};
Array.from(obj, function(value, index){
聽聽console.log(value, index, this, arguments.length);
聽聽return value.repeat(3); //蹇呴』鎸囧畾榪斿洖鍊鹼紝鍚﹀墶榪斿洖undefined
}, obj); |
鎵ц緇撴灉濡備笅锛?br >
鍙互鐪嬪埌鍔犲伐鍑芥暟鐨則his浣滅敤鍩熻obj瀵矽薄鍙栦唬锛屼篃鍙互鐪嬪埌鍔犲伐鍑芥暟榛樿鎷ユ湁涓や釜褰㈠弬锛屽垎鍒負榪唬鍣ㄥ綋鍓嶅厓緔犵殑鍊煎拰鍏剁儲寮曘€?/p>
娉ㄦ剰锛屼竴鏃︿嬌鐢ㄥ姞宸ュ嚱鏁幫紝蹇呴』鏄庣‘鎸囧畾榪斿洖鍊鹼紝鍚﹀墶灝嗛殣寮忚繑鍥瀠ndefined锛屾渶緇堢敓鎴愮殑鏁扮粍涔熶細鍙樻垚涓€涓彧鍖呭惈鑻ュ共涓猽ndefined鍏冪礌鐨勭┖鏁扮粍銆?/p>
瀹為檯涓婏紝濡傛灉涓嶉渶瑕佹寚瀹歵his锛屽姞宸ュ嚱鏁板畬鍏ㄥ彲浠ユ槸涓€涓澶村嚱鏁般€備笂榪頒唬鐮佸彲浠ョ畝鍖栧涓嬶細
Array.from(obj, (value) => value.repeat(3)); |
闄や簡涓婅堪obj瀵矽薄浠ュ锛屾嫢鏈夎凱浠ｅ櫒鐨勫璞¤繕鍖呮嫭榪欎簺锛歋tring锛孲et锛孧ap锛宎rguments 絳夛紝Array.from緇熺粺鍙互澶勭悊銆傚涓嬫墍紺猴細
// StringArray.from('abc'); // ["a", "b", "c"]
// SetArray.from(new Set(['abc', 'def'])); // ["abc", "def"]
// MapArray.from(new Map([[1, 'abc'], [2, 'def']])); // [[1
, 'abc'], [2, 'def']]
// 澶╃敓鐨勭被鏁扮粍瀵矽薄argumentsfunction fn(){
聽聽return Array.from(arguments);
}fn(1, 2, 3); // [1, 2, 3]
|
鍒拌繖浣犲彲鑳戒互涓篈rray.from灝辮瀹屼簡锛屽疄闄呬笂榪樻湁涓€涓噸瑕佺殑鎵╁睍鍦烘櫙蹇呴』鎻愪笅銆傛瘮濡傝鐢熸垚涓€涓粠0鍒版寚瀹氭暟瀛楃殑鏂版暟緇勶紝Array.from灝卞彲浠ヨ交鏄撶殑鍋氬埌銆?/p>
Array.from({length: 10}, (v, i) => i); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
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| Chrome | Firefox | Edge | Opera | Safari |
|---|---|---|---|---|
| 45+ | 32+ | 9.0+ |
Array.isArray
欏懼悕鎬濅箟锛孉rray.isArray鐢ㄦ潵鍒ゆ柇涓€涓彉閲忔槸鍚︽暟緇勭被鍨嬨€侸S鐨勫急綾誨瀷鏈哄埗瀵艱嚧鍒ゆ柇鍙橀噺綾誨瀷鏄垵綰у墠絝紑鍙戣€呴潰璿曟椂鐨勫繀鑰冮锛屼竴鑸垜閮戒細灝嗗叾浣滀負鑰冨療鍊欓€変漢絎竴棰橈紝鐒跺悗鍩轟簬姝ゅ睍寮€銆傚湪ES6鎻愪緵璿ユ柟娉曚箣鍓嶏紝ES5鑷衝皯鏈夊涓?縐嶆柟寮忓垽鏂竴涓€兼槸鍚︽暟緇勶細
var a = [];
// 1.鍩轟簬instanceofa instanceof Array;
// 2.鍩轟簬constructora.constructor === Array;// 3.鍩轟簬Object.prototype.isPrototypeOfArray.prototype.isPrototypeOf(a);// 4.鍩轟簬getPrototypeOfObject.getPrototypeOf(a) === Array.prototype;// 5.鍩轟簬Object.prototype.toStringObject.prototype.toString.apply(a) === '[object Array]';
|
浠ヤ笂锛岄櫎浜哋bject.prototype.toString澶栵紝鍏跺畠鏂規硶閮戒笉鑳芥紜垽鏂彉閲忕殑綾誨瀷銆?/p>
瑕佺煡閬擄紝浠ｇ爜鐨勮繍琛岀幆澧冨嶮鍒嗗鏉傦紝涓€涓彉閲忓彲鑳戒嬌鐢ㄦ祽韜В鏁板幓榪鋒儜瀹冪殑鍒溳€犺€呫€備笖鐪嬶細
var a = {
聽聽__proto__: Array.prototype
};// 鍒嗗埆鍦ㄦ帶鍒跺彴璿曡繍琛屼互涓嬩唬鐮?/code>// 1.鍩轟簬instanceofa instanceof Array; // true
// 2.鍩轟簬constructora.constructor === Array; // true
// 3.鍩轟簬Object.prototype.isPrototypeOfArray.prototype.isPrototypeOf(a); // true
// 4.鍩轟簬getPrototypeOfObject.getPrototypeOf(a) === Array.prototype; // true
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浠ヤ笂锛?縐嶆柟娉曞皢鍏ㄩ儴榪斿洖true锛屼負浠€涔堝憿锛熸垜浠彧鏄墜鍔ㄦ寚瀹氫簡鏌愪釜瀵矽薄鐨刜_proto__灞炴€т負Array.prototype锛屼究瀵艱嚧浜嗚瀵矽薄緇ф壙浜咥rray瀵矽薄锛岃繖縐嶆涓嶈礋璐ｄ換鐨勭戶鎵挎柟寮忥紝浣垮緱鍩轟簬緇ф壙鐨勫垽鏂柟妗堢灛闂村湡宕╃摝瑙ｃ€?/p>
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鍥炲埌ES6锛屼嬌鐢ˋrray.isArray鍒欓潪甯哥畝鍗曪紝濡備笅锛?a href="https://web.mit.edu/jwalden/www/isArray.html" target="_blank" >Determining with absolute accuracy whether or not a JavaScript object is an array
最後更新：2017-08-19 10:02:35