浠€涔堟槸鍙橀噺鎻愬崌锛熷畾涔夛細鍙橀噺鎻愬崌鏄寚褰撴爤鍐呭瓨浣滅敤鍩熷舰鎴愭椂锛屽湪JS浠ｇ爜鎵ц涔嬪墠锛屾祻瑙堝櫒浼氶鍏堢敤var鍜宖unction鍏抽敭瀛楀０鏄庡彉閲忥紙榛樿鍊间负undefined锛夛紝definedefined锛堝嵆璧嬪€兼搷浣滐級锛岃繖绉嶉澶勭悊鏈哄埗绉颁负鍙橀噺鎻愬崌鏈哄埗锛屼篃绉颁负棰勫畾涔夈€傜敱浜庝唬鐮佽繃澶氱矘璐达紝闄勬枃涓婁笅鏂囧涓嬶細1.鍙橀噺鎻愬崌鏈塚ar澹版槑鍜屾病鏈塚ar澹版槑鐨勫尯鍒細var杩愮畻绗﹀畾涔夌殑鍙橀噺浼氭垚涓哄寘鍚殑鍑芥暟鐨勫眬閮ㄥ彉閲忓畠銆備絾鏄紝鎮ㄥ彲浠ラ€氳繃鍦ㄥ嚱鏁板唴閮ㄥ畾涔夊彉閲忔椂鐪佺暐var杩愮畻绗︽潵瀹氫箟鍏ㄥ眬鍙橀噺銆傚嚱鏁癴oo(){a=0;varb=0;}foo()console.log(a);//0console.log(b);//UncaughtReferenceError:bisnotdefinedvara=b=12//杩欓噷鐨刡涔熸槸娌℃湁var鐨?/*绛変环浜巚ara=12;b=12*/var澹版槑鐩稿叧鍙橀噺鎻愬崌缁冧範--1:console.log(a,b)vara=12,b='灏忕櫧'functionfoo(){console.log(a,b)vara=b=13console.log(a,b)}foo()console.log(a,b)/*output:undefinedundefinedundefined"灏忕櫧"13131213*/瑙ｉ噴--1:1)a鍜宐鏄瓑浠风殑瀹氫箟涓や釜绐楀彛鍙橀噺銆傚彉閲忓湪浠ｇ爜鎵ц鍓嶅畾涔変絾鏈祴鍊硷紝鎵€浠ユ鏃舵湭瀹氫箟锛?锛夊綋浠ｇ爜鎵ц鍒板嚱鏁版椂锛岀涓€涓帶鍒跺彴銆俵og(a,b)鏃讹紝鎻愬崌浜嗗嚱鏁颁腑灞€閮ㄥ彉閲廰鐨勫畾涔夛紝浣嗘病鏈夊０鏄巄锛屾墍浠ヤ綔鐢ㄥ煙閾剧殑褰撳墠娲诲姩瀵硅薄锛堝嚱鏁颁笂涓嬫枃锛夋壘涓嶅埌b鐨勫０鏄庯紝浜庢槸瀵绘壘涓嬩竴涓寘鍚笂涓嬫枃鐨勬椿鍔ㄥ璞★紝鎵惧埌b='Xiaobai'锛屾墍浠ユ鏃舵墦鍗皍ndefined"Xiaobai"锛?锛夋墽琛寁ara=b=13鏃讹紝鍒嗗埆缁欏嚱鏁板眬閮ㄥ彉閲廰鍜屽叏灞€鍙橀噺b璧嬪€煎悗锛屾墦鍗板嚭鐨勫€间负1313锛?锛夌敱浜庡嚱鏁拌祴鍊肩殑鍙橀噺a鏄眬閮ㄥ彉閲忥紝b鏄叏灞€鍙橀噺锛屾鏃舵墦鍗扮殑a鍜宐閮芥槸鍏ㄥ眬鍙橀噺锛屾墍浠鐨勫€间笉鍙橈紝b鐨勫€艰祴鍊紀f13,soprint1213;var澹版槑鐩稿叧鍙橀噺鎻愬崌缁冧範--2:console.log(a,b)vara=12,b='灏忕櫧'functionfoo(){console.log(a,b)}foo()鎺у埗鍙般€俵og(a,b)/*Output:undefinedundefined12"Xiaobai"12"Xiaobai"*/瑙ｉ噴--2:1)var鍙橀噺澹版槑琚彁鍗囧埌鏈€涓婇潰锛屼絾鏄病鏈夎祴鍊硷紝鎵€浠ユ墦鍗颁负undefinedundefined2)鑾峰彇鍏ㄥ眬鍙橀噺3)鑾峰彇鍏ㄥ眬鍙橀噺var澹版槑鐩稿叧鍙橀噺鎻愬崌缁冧範--3:a=2functionfoo(){vara=12;b='灏忕櫧'console.log('b'inwindow)console.log(a,b)}foo()console.log(b)console.log(a)/*Output:true12'Xiaobai'Xiaobai2*/瑙ｉ噴--3:1)b娌℃湁浣跨敤var杩愮畻绗﹀０鏄?鎵€浠ラ粯璁ゅ畾涔墂indow鍙橀噺,鎵€浠ユ墦鍗皌rue2)鍑芥暟鎵ц杩囩▼涓?浼氬皢褰撳墠娲诲姩瀵硅薄鍘嬪叆浣滅敤鍩熼摼鐨勯《绔?鍦ㄤ綔鐢ㄥ煙涓粠褰撳墠娲诲姩瀵硅薄寮€濮嬫煡鎵惧彉閲忛摼銆傚鏋滄壘涓嶅埌锛屽氨鍥炲幓鎵句笅涓€涓椿鍔ㄥ璞″寘鍚笂涓嬫枃锛屾墍浠ユ鏃舵墦鍗扮殑a鏄?2锛?锛夊湪鍑芥暟澶栨墦鍗板彉閲廰銆乥锛屽垯褰撳墠涓婁笅鏂囩殑娲诲姩瀵硅薄涓簑indow瀵硅薄锛屾墍浠ュ叏灞€鍙橀噺a銆乥锛涙墦鍗皏ar澹版槑鐩稿叧鍙橀噺鎻愬崌缁冧範--4:fn();鎺у埗鍙版棩蹇楋紙v1锛夛紱鎺у埗鍙版棩蹇楋紙v2锛夛紱鎺у埗鍙版棩蹇楋紙v3锛夛紱鍑芥暟fn(){varv1=v2=v3=2019;鎺у埗鍙版棩蹇楋紙v1锛夛紱鎺у埗鍙版棩蹇楋紙v2锛夛紱鎺у埗鍙版棩蹇楋紙v3锛夛紱}/*杈撳嚭201920192019UncaughtReferenceError:v1isnotdefined*/瑙ｉ噴--4:1)鍑芥暟澹版槑涔熸彁鍗囦簡锛屾墍浠?019銆?019銆?019閮芥槸鍑芥暟涓墦鍗扮殑灞€閮ㄥ彉閲忋€傚嚱鏁版墽琛屽悗锛寃indow娲诲姩瀵硅薄涓病鏈夊畾涔塿1銆乿2銆乿3锛屾墍浠ユ鏃舵姤閿?.绛夊彿宸﹁竟鐨勫彉閲忔彁鍗?琛ㄧず璧嬪€硷紝鎵€浠ュ乏杈瑰簲璇ユ槸鍙橀噺锛屽彸杈瑰簲璇ユ槸鍊硷紝鎵€浠ュ彧鍦ㄧ瓑鍙峰乏杈硅繘琛屽彉閲忔彁鍗?绛夊彿宸﹁竟鐨勫彉閲忔彁鍗囩粌涔?-1:print()functionprint(){console.log('灏忕櫧')}print()/*Output:XiaobaiXiaobai*/Explanation--1:1)鍥犱负function鍏抽敭瀛椾篃鎻愬崌浜嗗彉閲忥紝鎵€浠ヤ笉闅剧悊瑙ｇ浉褰撲簬璋冪敤浜嗕袱娆rint()鏂规硶锛屾墍浠ユ墦鍗颁簡涓ゆ灏忕櫧锛涚瓑鍙峰乏杈圭殑鍙橀噺鎻愬崌缁冧範--2:console.log(printf)//undefinedprintf()//Errorvarprintf=function(){console.log('鏋椾緷渚?)}printf()//Unexecuted/*OutputundefinedUncaughtTypeError:printisnotafunction*/瑙ｉ噴--2:1)涔熸槸鐢变簬鍙橀噺鎻愬崌鏈哄埗涓巚arprint鐨勫垵濮嬪€兼槸undefined2)鍥犱负1),鑰屽湪杩檛ime,printf浣滀负鍑芥暟娌℃湁琚祴鍊硷紝鎵€浠ユ鏃秔rint()涓嶆槸鍑芥暟锛屾墍浠ユ姤绫诲瀷閿欒TypeError绛夊彿宸﹁竟鐨勫彉閲忔彁鍗囩粌涔?-3:varfn=functionsum(){console.log(sum);//=>鍑芥暟鏈韩console.log(1);//=>1}//sum();//=>UncaughtReferenceError:sumisnotdefinedfn();/*杈撳嚭锛毱抯um(){console.log(sum);//=>functionitselfconsole.log(1);//=>1}1*/Explanation--3:1)sum()鏄尶鍚嶅嚱鏁扮殑鍏蜂綋鍚嶇О锛屽彧鑳藉湪鍑芥暟涓婁笅鏂囦腑浣跨敤锛屽洜姝ゅ湪鍖呭惈涓婁笅鏂囦腑璁块棶浼氭姤閿欙紱2锛塮n鐨勫畾涔夋彁鍗囧苟鍒濆鍖栦负undefined鍚庯紝浼氫竴鐩存墽琛屽埌sum()鍐嶆涓篺n璧嬪€硷紝璋冪敤sum鎵嶈兘姝ｅ父杈撳嚭銆?.鏉′欢鍒ゆ柇涓嬬殑鍙橀噺鎻愬崌鍦ㄥ綋鍓嶄綔鐢ㄥ煙涓紝鏃犺鏉′欢鏄惁鎴愮珛锛岄兘蹇呴』杩涜鍙橀噺鎻愬崌銆傚湪鑰佺増鏈祻瑙堝櫒锛圛E10浠ヤ笅锛夌殑娓叉煋鏈哄埗涓嬶紝鍑芥暟鐨勫０鏄庡拰瀹氫箟閮芥槸澶勭悊鐨勶紝浣嗘槸涓轰簡杩庡悎es6Block浣滅敤鍩燂紝鏂扮増鏈祻瑙堝櫒鍙湪鏉′欢鍒ゆ柇涓０鏄庡嚱鏁帮紝涓嶇鏉′欢鏄惁涓虹湡锛屽苟娌℃湁绫讳技var鐨勫畾涔夈€傚悓鏃讹紝濡傛灉鍒ゆ柇浣撲腑鍑虹幇浜唋et銆乧onst銆乫unction锛屽氨浼氬垱寤轰竴涓柊鐨勬墽琛屼笂涓嬫枃锛屽嵆鍧楃骇涓婁笅鏂囥€傛潯浠跺垽鏂笅鐨勫彉閲忔彁鍗囩粌涔狅紙鍙橀噺鎻愬崌鍜屽嚱鏁版彁鍗囩殑鍖哄埆锛?-1锛歝onsole.log(a);//鏈畾涔夌殑console.log(b);//鏈畾涔塱f(true){console.log(a);//鏈畾涔夌殑鍙橀噺a=1;鎺у埗鍙版棩蹇楋紙b锛夛紱//茠b(){console.log("1");}functionb(){console.log("1");}}console.log(a);//1console.log(b());//1,undefined/*杈撳嚭锛歶ndefinedundefined茠b(){console.log("1");}11undefined//鍥犱负鍑芥暟b()娌℃湁杩斿洖鍊硷紝console.log(b())锛宐()鎵ц鏃舵墦鍗?锛屾墽琛屽畬鎵撳嵃undefined銆?/Explanation--1:1)鍦ㄥ綋鍓嶄綔鐢ㄥ煙鍐咃紝鏃犺鏉′欢鏄惁涓虹湡锛岄兘瑕佽繘琛屽彉閲忔彁鍗囷紝涓轰簡杩庡悎es6涓殑鍧椾綔鐢ㄥ煙锛屾柊鐗堟祻瑙堝櫒鍙０鏄庡嚱鏁板湪鏉′欢鍒ゆ柇涓紝涓嶇鏉′欢鏄惁涓虹湡锛岄兘娌℃湁浠讳綍浠峰€笺€傚洜姝わ紝a鍜宐閮芥墦鍗版湭瀹氫箟銆?锛夊湪鎵ц鍒癷f(){}璇彞鍧楁椂锛岀洿鍒版墽琛屽畬璧嬪€艰鍙ユ墠瀵瑰彉閲忚祴鍊硷紝鐩存帴璧嬪€肩粰鍑芥暟銆?锛夊鏋滄墽琛岀粨鏉燂紝鍒欒祴鍊兼搷浣滅粨鏉燂紝鎵€浠ュ彲浠ユ墦鍗癮,b()锛涙潯浠跺垽鏂笅鐨勫彉閲忔彁鍗囩粌涔狅紙鍙橀噺鎻愬崌锛?-2:console.log(a)if(true){console.log(a)vara='灏忕櫧'}console.log(a)/*杈撳嚭undefinedundefined灏忕櫧/Explanation--2:1锛変笉绠℃潯浠舵槸鍚︿负鐪燂紝鍙橀噺閮戒細琚彁鍗囷紝鎵€浠ヤ細鎵撳嵃undefined锛?锛夐噸鏂拌祴鍊兼墦鍗癮锛涙潯浠跺垽鏂笅鐨勫彉閲忔彁鍗囩粌涔?-3://console.log(f)//UncaughtReferenceError:fisnotdefinedif(functionf(){}){console.log(typeoff)//undefined}瑙ｉ噴--3:1)if涓?)涓殑琛ㄨ揪寮忎笉浼氳鎻愬崌锛?锛夊垽鏂殑鏉′欢娌℃湁鎻愬崌锛屾墍浠ユ潯浠堕噷闈㈢殑f鏄痷ndefined銆備粩缁嗘瘮杈冧笅闈㈢殑浠ｇ爜锛?log(globalPrint)//茠globalPrint(){}console.log(fatherPrint)//茠fatherPrint(){}console.log(childPrint)//undefinedfunctionfatherPrint(){}if(false){console.log(globalPrint)//console.log(fatherPrint)//console.log(childPrint)//functionchildPrint(){console.log(1)//return"childPrint()鐨勮繑鍥炲€?;}}}console.log(childPrint)//undefinedconsole.log(globalPrint)//茠globalPrint(){}console.log(fatherPrint)//undefinedconsole.log(childPrint)//undefinedfunctionglobalPrint(){}if(true){console.log(globalPrint)//茠globalPrint(){}console.log(fatherPrint)//茠fatherPrint(){}console.log(childPrint)//undefinedfunctionfatherPrint(){}if(true){console.log(globalPrint)//茠globalPrint(){}console.log(fatherPrint)//茠fatherPrint(){}console.log(childPrint)//茠childPrint(){console.log(1)return"childPrint()杩斿洖鍊?;}functionchildPrint(){console.log(1)//1return"childPrint()杩斿洖鍊?;}}}console.log(childPrint())//childPrint()杩斿洖鍊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