PromisePromise鏄疎S6涓紓姝ョ紪绋嬬殑涓€绉嶈В鍐虫柟妗堬紝姣斾紶缁熺殑瑙ｅ喅鏂规鈥斺€斿洖璋冨嚱鏁板拰浜嬩欢鏇村悎鐞嗐€佹洿寮哄ぇ銆侾romise鏄竴涓璞★紝鎻愪緵浜嗙粺涓€鐨凙PI锛屽悇绉嶅紓姝ユ搷浣滃彲浠ョ敤鍚屾牱鐨勬柟寮忓鐞嗐€侾romise鎿嶄綔鍙細澶勪簬涓夌鐘舵€佷箣涓€锛氬緟澶勭悊銆佸凡瑙ｅ喅鍜屽凡鎷掔粷銆侾romise鐨勭姸鎬佸彧浼氫粠鏈畬鎴愮姸鎬佸彉涓哄畬鎴愮姸鎬佹垨澶辫触鐘舵€併€傜姸鎬佷竴鏃﹁浆鍙橈紝灏辨棤娉曟敼鍙樸€傛洿澶歅romise鍩虹鐭ヨ瘑璇疯烦杞埌闃竴宄?Es6Promise鎵嬪姩瀹炵幇涓€涓狿romise杩欏勾澶达紝鎵嬪姩瀹炵幇涓€涓狿romise宸茬粡鏄潰璇曠殑甯歌鎿嶄綔浜嗐€傛帴涓嬫潵锛屼负浜嗘洿濂界殑鐞嗚ВPromise锛屾垜浠氨鏉ealize瀹冿紱Promise鏈夌粺涓€鐨勮鑼冿紝鐩殑鏄负浜嗚澶у瀹炵幇鐨刾romise鏇村ソ鐨勫疄鐜板吋瀹规€э紝鎵€浠ュ嚭鐜颁簡Promises/A+瑙勮寖锛涙帴涓嬫潵鐨刾romises閮芥槸鎸夌収Promises/A+瑙勮寖瀹炵幇鐨凱romises鍥犱负绫绘湁涓夌鐘舵€侊紝鎵€浠ュ厛澹版槑涓変釜甯搁噺鏉ヨ〃绀虹姸鎬乧onstPENDING='pending';constFULFILLED='宸插畬鎴?;constREJECTED='鎷掔粷';鍐欎竴涓狿romise绫籧lassPromise{constructor(executor){//褰㈠紡鍙傛暟楠岃瘉if(typeofexecutor!=='function')thrownewTypeError(`Promiseresolver${executor}isnotafunction`)//鍒濆鍖栬繖涓€傜姸鎬?寰呭鐞嗭紱//鐘舵€乼his.value=null;//鏈€缁堝€紅his.reason=null;//鎷掔粷鍘熷洜//鎵цcbexecutor();}}鐒跺悗鎴戜滑闇€瑕佸湪Promise鐨勫舰鍙傛墽琛屽櫒涓坊鍔爎esolve鍜宺eject涓や釜褰㈠弬鍑芥暟锛涙牴鎹畾涔夛紝瀹冧滑鏄敱JS寮曟搸鎻愪緵鐨勶紝鎵€浠ユ垜浠渶瑕佹彁鍓嶅畾涔塩lassPromise{constructor(executor){...//bindthisinresolveandrejecttothePromiseinstance+this.resolve=this.瑙ｅ喅.bind(this);+this.reject=this.reject.bind(this);//executecb+try{+executor(this.resolve,this.reject);+}catch(e){this.reject(e)}}resolve(val){//鍒ゆ柇褰撳墠鐘舵€侊紝鍙兘鎵ц澶勪簬绛夊緟鐘舵€乮f(this.status===PENDING){this.status=FULFILLED;//鐘舵€佹敼鍙榯his.value=val;//鏈€缁堣祴鍊紏}reject(err){if(this.status===PENDING){this.status=REJECTED;this.reason=閿欒锛泒}}褰損romise瀹炰緥璋冪敤鍐呴儴鍑芥暟resolve鎴杛eject鏃讹紝璋冪敤鐨勫叾瀹炴槸涓€涓尶鍚嶅嚱鏁帮紝鏃犳硶鑾峰彇鍑芥暟涓璽his.status鐨勫€硷紝鎵€浠ラ渶瑕佹彁鍓嶇敤bind杩涜缁戝畾锛涘綋promise瀹炰緥鐨勬墽琛岃€呮湰韬姏鍑哄紓甯告椂锛孭romise浼氬皢寮傚父鏀惧叆reject鍑芥暟涓幓澶勭悊锛屾墍浠ユ坊鍔爐ry{...}catch(e){...}鏉ュ鐞嗚繖绉嶆儏鍐点€傚垵姝ュ疄鐜扮劧鍚庢帴鏀朵袱涓洖璋冨嚱鏁般€俹nFulfilled鏄綋promise瀹炰緥鐨勭姸鎬佸彉涓篺ulfilled鏃惰皟鐢ㄧ殑鍑芥暟銆俹nRejected鏄疄渚嬬姸鎬佸彉涓烘嫆缁濇椂璋冪敤鐨勫嚱鏁帮紝鐒跺悗杩斿洖涓€涓柊鐨刾romise瀹炰緥锛涜繖閲屼娇鐢╯etTimeout鏉ユā鎷烶romise閲岄潰鐨勫井浠诲姟寮傛绫籔romise{...then(onFulfilled,onRejected){//鍙傛暟妫€鏌nFulfilled,onRejected鏄彲閫夌殑褰㈠弬onFulfilled=typeofonFulfilled!=='function'?val=>val:onFulfilled;onRejected=typeofonRejected!=='鍑芥暟'?鍘熷洜=>{鎶涘嚭鍘熷洜}:onRejected;if(this.status===FULFILLED){//setTimeout妯℃嫙寰换鍔″紓姝etTimeout(()=>{try{//閲嶆柊鍔犲叆try-catch锛宻ettimeout鏄紓姝ョ殑锛屼笉鑳借閲岄潰鐨則ry-catch鎹曡幏澶栭儴鏋勯€犲嚱鏁皁nFulfilled(this.value);//浠ユ渶缁堝€间綔涓哄弬鏁版墽琛宱nFulfilled鍑芥暟}catch(e){reject(e)}})}if(this.status===REJECTED){//鎵цonRejected鍑芥暟setTimeout(()=>{try{onRejected(this.reason);}catch(e){reject(e)}});}}}then淇敼鏍规嵁涓婇潰鐨勫啓娉曪紝濡傛灉resolve鍦ㄦ垜浠琾romise瀹炰緥鐨別xecutor涓槸寮傛瀹炵幇锛岄偅涔坱hen鏂规硶灏变笉鑳借揪鍒板師鏉ョ殑鏁堟灉newPromise((resolve,reject)=>{setTimeout(()=>{resolve(1)})}).then(val=>console.log(val),//output1err=>console.log(err))姝ゆ椂鎴戜滑鑷繁鐨刾romise渚嬪瓙鏃犳硶姝ｇ‘杈撳嚭1銆傚師鍥犳槸褰撳紓姝ユ墽琛屾墽琛屽櫒涓殑鐘舵€佹敼鍙橈紙resolve/reject锛夋椂锛屽悓姝ヨ皟鐢ㄤ簡then鍑芥暟銆傛鏃秔romise鐨勭姸鎬佽繕鏄痯ending鐘舵€侊紝涓嶈兘璋冪敤浠讳綍鍑芥暟锛涙墍浠ユ垜浠湁蹇呰鍦╰hen涓姞鍏ending鐘舵€佺殑澶勭悊锛涢噰鐢ㄨ闃呭拰鍙戝竷鐨勬柟寮忚В鍐崇姸鎬佸紓姝ュ彉鍖朿lassPromise{constructor(executor){...//鍒濆鍖?..+this.onFulfilledCbs=[];//鎴愬姛鍥炶皟鍑芥暟queue+this.onRejectedCbs=[];//澶辫触鍥炶皟鍑芥暟闃熷垪...}resolve(val){if(this.status===PENDING){...//涓€鏃︾姸鎬佹敼鍙橈紝閬嶅巻鍑芥暟闃熷垪锛屼互鏈€缁堝€间綔涓哄弬鏁拌Е鍙戦槦鍒椾腑鐨勫嚱鏁?this.onFulfilledCbs.forEach(fn=>fn(this.value));}}reject(err){if(this.status===PENDING){...+this.onRejectedCbs.forEach(fn=>fn(this.reason));}}then(onFulfilled,onRejected){...//褰撶姸鎬佷负pending+if(this.status===PENDING){+//娣诲姞寰换鍔″洖璋冨嚱鏁板埌鍑芥暟闃熷垪+this.onFulfilledCbs.push(value=>{+setTimeout(()=>{+try{+onFulfilled(value)+}catch(e){reject(e)}+})+});++this.onRejectedCbs.push((鍘熷洜)=>{+setTimeout(()=>{+try{+onRejected(reason)+}catch(e){reject(e)}+})+});+}}}杩欐牱褰損romise瀹炰緥鐨勭姸鎬佸紓姝ユ洿鏀癸紝鐒跺悗鏄柟娉曚篃鑳芥纭Е鍙戦摼寮忚皟鐢ㄣ€備箣鍓嶈杩囷紝then鏂规硶浼氳繑鍥炰竴涓柊鐨刾romise瀹炰緥锛岃繖涓疄渚嬬殑鍊煎彲浠ラ€氳繃then鏃犻檺璋冪敤鏃犻檺浼犻€掍笅鍘汇€備负浜嗗疄鐜拌繖涓柟娉曪紝鎴戜滑闇€瑕佸湪then涓繑鍥炰竴涓猵romiseNewpromiseinstancethen(onFulfilled,onRejected){...//鍒涘缓涓€涓柊鐨刾romise瀹炰緥+letpromise2=newPromise((resolve,reject)=>{//鍚屾鎿嶄綔锛堝垵濮嬬姸鎬佸彉涓哄悓姝ワ級if(this.status===FULFILLED){...}if(this.status===REJECTED){...}if(this.status===PENDING){...}+})+returnpromise2}閭ｆ垜浠湪鏂扮殑promise2涓€庝箞璋冪敤resolve鍜宺eject鍛紵鏈畾锛屽弬鑰冭鑼冩牴鎹甈romises/A+瑙勮寖锛屾垜浠皢onFulfilled(value)鍜宱nRejected(reason)鐨勭粨鏋滃畾涔変负x锛屽皢鍏跺拰promise2浼犲叆涓€涓柊鍑芥暟resolvePromise杩涜澶勭悊锛涜繖閲屾垜浠娇鐢ㄨ繖涓猲ew澶勭悊鍑芥暟瀹氫箟涓哄父閲忓嚱鏁?/@params//$pomise2-newpromise甯搁噺//$x-onFulfilled/onRejected澶勭悊缁撴灉//$resolve-resolvefunctioninpromise2//$reject-rejectfunctionconstinpromise2RESOLVEPROMISE=function(promise2,x,resolve,reject){...}鐒跺悗閲嶅啓then鏂规硶then(onFulfilled,onRejected){...//杩斿洖涓€涓柊瀹炰緥瀹炵幇閾惧紡璋冪敤letpromise2=newPromise((resolve,reject)=>{if(this.status===FULFILLED){setTimeout(()=>{try{//浠ユ渶缁堝€间綔涓哄弬鏁版墽琛宱nFulfilled鍑芥暟+letx=onFulfilled(this.value);//鍒嗘瀽鎵ц缁撴灉x涓巔romise鐨勫叧绯?RESOLVEPROMISE(promise2,x,resolve,reject);}catch(e){reject(e)}})}if(this.status===REJECTED){setTimeout(()=>{try{+璁﹛=onRejected(this.reason)+RESOLVEPROMISE(promise2,x,resolve,reject);}catch(e){reject(e)}});}if(this.status===PENDING){this.onFulfilledCbs.push(value=>{setTimeout(()=>{try{+letx=onFulfilled(value)+RESOLVEPROMISE(promise2,x,resolve,reject);}catch(e){reject(e)}})});this.onRejectedCbs.push((reason)=>{setTimeout(()=>{try{+letx=onRejected(reason)+RESOLVEPROMISE(promise2,x,resolve,reject);}catch(e){reject(e)}})});}})returnpromise2}瀹炵幇resolvePromise鍑芥暟鏍规嵁瑙勮寖锛宺esolvePromise瑙勫垯澶ц嚧濡備笅锛歱romise2鍜寈鎸囧悜鍚屼竴涓璞★紝鎶涘嚭绫诲瀷閿欒銆傚鏋渪鏄疨romise绫伙紝鍒欏畠鐨勭姸鎬佽鎺ュ彈銆傚苟鐩稿簲鐨勬墽琛屽叾resolve鎴杛eject鍑芥暟x鏄嚱鏁版垨瀵硅薄x.then鏄嚱鏁帮紝璋冪敤x.then鏂规硶锛岄€掑綊缁撴灉x.then涓嶆槸鍑芥暟锛岃皟鐢ㄤ笂闈㈢殑resolve涓嶆槸锛岃皟鐢╮esolveconstRESOLVEPROMISE=function(promise2,x,resolve,reject){//x绛変簬promise2->鎶ュ憡閿欒if(promise2==x){returnreject(newTypeError('Chainingcycledetectedforpromise'))}letcalled;//闃叉澶氭鎴愬姛璋冪敤鍜屽け璐?/x鏄竴涓猵romise绫籭f(xinstanceofPromise){x.then(value=>{Promise.resolvePromise(promise2,value,resolve,reject);},err=>{reject(err)})//x鏄嚱鏁拌繕鏄璞elseif(x!==null&&typeofx=='object'||typeofx=='function'){try{//鍙杧.then鍙兘鎶ラ敊//ifxhasthen鏂规硶letthen=x.then;//ifthen鏄竴涓嚱鏁癷f(typeofthen=='function'){//浣跨敤call璋冪敤then鏂规硶鎸囧悜x锛岄槻姝㈠啀娆″彇x.then鎶ラ敊then.call(x,value=>{if(called)return;called=true;Promise.resolvePromise(promise2,value,resolve,reject);},err=>{if(called)return;called=true;reject(err)})//then涓嶆槸鍑芥暟}else{if(called)return;绉颁负=鐪燂紱瑙ｅ喅锛坸锛夛紱}}catch(e){if(called)returncalled=truereject(e)}}else{//x涓哄熀鏈被鍨嬪€紃esolve(x);}}鑷虫锛屾垜浠殑Promise灏卞熀鏈疄鐜颁簡锛岄櫎浜唗hen鏂规硶浠ュ鐨勬柟娉曡繖閲屽氨涓嶄竴涓€瀹炵幇浜嗭紱鍙互鍏ㄥ眬瀹夎涓€涓彃浠讹紝娴嬭瘯鑷繁瀹炵幇鐨凱romise鏂囦欢鏄惁绗﹀悎瑙勮寖npminstall-gpromises-aplus-tests鐒跺悗鍦ㄦ枃浠舵湯灏炬坊鍔狅紝鍙傝€冩彃浠舵帴鍙ｉ獙璇丳romise.defer=Promise.deferred=function(){letdfd={};dfd.promise=newPromise((resolve,reject)=>{dfd.resolve=resolve;dfd.reject=reject;})returndfd;}module.exports=Promise;鏈€鍚庡湪缁堢杈撳叆鍛戒护鏌ョ湅鏂囦欢promises-aplus-tests[[浣犵殑Promise鏂囦欢鍚?js]]婧愮爜娆㈣繋绉绘鏈枃婧愮爜鏈€鍚庨檮涓婁竴涓鍚圥romise鐨凱romise/A+瑙勮寖瀹炵幇銆傚笇鏈涜兘甯姪澶у鏇存竻妤氱殑浜嗚ВPromise銆傛劅璋㈤槄璇伙紝娆㈣繋鎸囨銆傝璁吼煒€鍚勪綅璇昏€咃紝娆㈣繋star馃専
