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涓昏錛堝熀鏈級鏁版嵁綾誨瀷鏄細
- 瀛楃涓?
- 鏁板€?
- 甯冨皵
澶嶅悎錛堝紩鐢級鏁版嵁綾誨瀷鏄細
- 瀵硅薄
- 鏁扮粍
鐗規畩鏁版嵁綾誨瀷鏄細
- Null
- Undefined
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"Happy am I; from care I鈥檓 free!"
'"Avast, ye lubbers!" roared the technician.'
"42"
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璇鋒敞鎰忥紝JScript 涓病鏈夎〃紺哄崟涓瓧絎︾殑綾誨瀷錛堝 C++ 鐨?char錛夈€傝琛ㄧず Jscript 涓殑鍗曚釜瀛楃錛屽簲鍒涘緩涓€涓彧鍖呭惈涓€涓瓧絎︾殑瀛楃涓層€傚寘鍚浂涓瓧絎︼紙""錛夌殑瀛楃涓叉槸絀猴紙闆墮暱搴︼級瀛楃涓層€?/font>
鏁板€兼暟鎹被鍨?/font>
鍦?Jscript 涓暣鏁板拰嫻偣鍊兼病鏈夊樊鍒紱JScript 鏁板€煎彲浠ユ槸鍏朵腑浠繪剰涓€縐嶏紙JScript 鍐呴儴灝嗘墍鏈夌殑鏁板€艱〃紺轟負嫻偣鍊?/font>錛夈€?/font>
鏁村瀷鍊?/font>
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鍔犲墠緙€鈥?x鈥濓紙闆跺拰x|X錛夎〃紺?16 榪涘埗鏁村瀷鍊箋€傚彲浠ュ寘鍚暟瀛?0 鍒?9錛屼互鍙婂瓧姣?A 鍒?F錛堝ぇ鍐欐垨灝忓啓錛夈€備嬌鐢ㄥ瓧姣?A 鍒?F 琛ㄧず鍗佽繘鍒?10 鍒?15 鐨勫崟涓暟瀛椼€傚氨鏄 0xF 涓?15 鐩哥瓑錛屽悓鏃?0x10 絳変簬 16銆?/font>
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嫻偣鍊?/font>
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娉ㄦ剰浠モ€?x鈥濇垨鈥?0鈥濆紑濮嬪茍鍖呭惈灝忔暟鐐圭殑鏁板皢鍙戠敓閿欒銆備互涓嬫槸 Jscript 涓暟瀛楃殑渚嬪瓙銆?/font>
| 鏁板瓧 | 鎻忚堪 | 絳変環鍗佽繘鍒舵暟 |
|---|---|---|
| .0001, 0.0001, 1e-4, 1.0e-4 | 鍥涗釜鐩哥瓑鐨勬誕鐐規暟銆?/font> | 0.0001 |
| 3.45e2 | 嫻偣鏁般€?/font> | 345 |
| 42 | 鏁存暟銆?/font> | 42 |
| 0378 | 鏁存暟銆傝櫧鐒剁湅璧鋒潵鏄叓榪涘埗鏁幫紙浠?寮€澶達級錛屼絾鏄?涓嶆槸鏈夋晥鐨勫叓榪涘埗鏁板瓧錛屾墍浠ヤ負鍗佽繘鍒舵暟銆?/font> | 378 |
| 0377 | 鍏繘鍒舵暣鏁般€傛敞鎰忓畠铏界劧鐪嬭搗鏉ユ瘮涓婇潰鐨勬暟鍙皬1錛屼絾瀹為檯鏁板€兼湁寰堝ぇ涓嶅悓銆?/font> | 255 |
| 0.0001 | 嫻偣鏁般€傝櫧鐒朵互闆跺紑澶達紝浣嗙敱浜庡甫鏈夊皬鏁扮偣鎵€浠ヤ笉鏄叓榪涘埗鏁般€?/font> | 0.0001 |
| 00.0001 | 閿欒銆備袱涓浂寮€澶磋〃紺轟負鍏繘鍒訛紝浣嗗叓榪涘埗鏁頒笉鑳藉甫鏈夊皬鏁伴儴鍒嗐€?/font> | N/A 錛堢紪璇戦敊璇級 |
| 0Xff | 鍗佸叚榪涘埗鏁存暟銆?/font> | 255 |
| 0x37CF | 鍗佸叚榪涘埗鏁存暟銆?/font> | 14287 |
| 0x3e7 | 鍗佸叚榪涘埗鏁存暟銆傛敞鎰忊€榚鈥欏茍涓嶈璁や負鎸囨暟銆?/font> | 999 |
| 0x3.45e2 | 閿欒銆傚崄鍏繘鍒舵暟涓嶈兘鏈夊皬鏁伴儴鍒嗐€?/font> | N/A 錛堢紪璇戦敊璇級 |
鍙﹀錛孞Script鍖呭惈鐗規畩鍊兼暟瀛椼€傚畠浠槸錛?
- NaN 錛堜笉鏄暟錛夈€傚綋瀵逛笉閫傚綋鐨勬暟鎹繘琛屾暟瀛﹁繍綆楁椂浣跨敤錛屼緥濡傚瓧絎︿覆鎴栨湭瀹氫箟鍊箋€?
- 姝ｆ棤絀峰ぇ銆傚湪JScript涓鏋滀竴涓鏁板お澶х殑璇濅嬌鐢ㄥ畠鏉ヨ〃紺恒€?
- 璐熸棤絀峰ぇ銆傚湪JScript涓鏋滀竴涓礋鏁板お澶х殑璇濅嬌鐢ㄥ畠鏉ヨ〃紺恒€?
- 姝?鍜岃礋0銆侸script鍖哄垎姝?鍜岃礋0銆?
Boolean鏁版嵁綾誨瀷
灝界瀛楃涓插拰鏁板瓧綾誨瀷鍙互鏈夋棤鏁頒笉鍚岀殑鍊鹼紝boolean 鏁版嵁綾誨瀷鍗村彧鏈変袱涓€箋€傚畠浠槸鏂囧瓧 true 鍜?false銆侭oolean鍊兼槸涓€涓湡鍊鹼紝瀹冭〃紺轟竴涓姸鎬佺殑鏈夋晥鎬э紙璇存槑璇ョ姸鎬佷負鐪熸垨鍋囷級銆?/font>
鑴氭湰涓殑姣旇緝閫氬父寰楀埌涓€涓?Boolean 緇撴灉銆傝€冭檻涓嬩竴琛?Jscript 浠ｇ爜銆?/font>
y = (x == 2000);
榪欓噷瑕佹瘮杈冨彉閲?x 鐨勫€兼槸鍚︿笌鏁板瓧 2000 鐩哥瓑銆傚鏋滅浉絳夛紝姣旇緝鐨勭粨鏋滀負 Boolean 鍊?true錛屽茍灝嗗叾璧嬬粰鍙橀噺 y銆傚鏋渪涓?000涓嶇瓑錛屽垯姣旇緝鐨勭粨鏋滀負boolean鍊?b>false銆?/font>
Boolean鍊煎湪緇撴瀯鎺у埗涓挨鍏舵湁鐢ㄣ€傚彲浠ュ皢鐩存帴鍒涘緩 boolean 鍊肩殑姣旇緝涓庣敤浣跨敤璇?boolean 鍊肩殑璇彞鐩哥粍鍚堛€傝€冭檻涓嬮潰鐨凧Script浠ｇ爜鑼冧緥銆?/font>
if (x == 2000)
z = z + 1;
else
x = x + 1;
褰?boolean 鍊間負 true 鏃訛紝Jscript 涓殑 if/else 璇彞鎵ц涓€涓搷浣滐紙榪欐牱錛寊 = z + 1錛夛紝鑰屽綋 boolean 鍊間負 false 鏃舵墽琛屽彟涓€涓搷浣滐紙x = x + 1錛夈€?/font>
鍙互浣跨敤浠繪剰琛ㄨ揪寮忎綔姣旇緝琛ㄨ揪寮忋€備換浣曞€間負0銆乶ull銆佹湭瀹氫箟鎴栫┖瀛楃涓茬殑琛ㄨ揪寮忚瑙ｉ噴涓?false銆傚叾浠栦換鎰忓€肩殑琛ㄨ揪寮忚В閲婁負 true銆備緥濡傦紝鍙互浣跨敤濡備笅琛ㄨ揪寮忥細
if (x = y + z) //榪欏彲鑳戒笉鏄兂瑕佺殑緇撴灉鈥?濡備笅錛?/font>
娉ㄦ剰涓婇潰鐨勪唬鐮佸茍涓嶆鏌?x 鏄惁涓?y+z 鐩哥瓑錛屽洜涓轟粎浣跨敤浜嗕竴涓瓑鍙鳳紙璧嬪€鹼級銆傜浉鍙嶇殑錛屼笂闈㈢殑浠ｇ爜灝?y+z 璧嬬粰鍙橀噺 x錛岀劧鍚庢鏌ユ暣涓〃杈懼紡鐨勫€兼槸鍚︿負闆躲€傝媯€鏌?x 鏄惁涓?y+z 鐩哥瓑錛屼嬌鐢ㄥ涓嬩唬鐮併€?/font>
if (x == y + z) // 榪欎笌涓婇潰鐨勪唬鐮佷笉鍚岋紒
Null 鏁版嵁綾誨瀷
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鍖呭惈 null 鐨勫彉閲忓寘鍚€滄棤鍊尖€濇垨鈥滄棤瀵硅薄鈥濄€傛崲鍙ヨ瘽璇達紝璇ュ彉閲忔病鏈変繚瀛樻湁鏁堢殑鏁般€佸瓧絎︿覆銆乥oolean銆佹暟緇勬垨瀵硅薄銆傚彲浠ラ€氳繃緇欎竴涓彉閲忚祴 null 鍊兼潵娓呴櫎鍙橀噺鐨勫唴瀹廣€?/font>
璇鋒敞鎰忥紝鍦?Jscript 涓紝null 涓?0 涓嶇浉絳夛紙涓庡湪 C 鍜?C++ 涓笉鍚岋級銆傚悓鏃跺簲璇ユ寚鍑虹殑鏄紝Jscript涓?typeof 榪愮畻絎﹀皢鎶ュ憡 null 鍊間負 Object 綾誨瀷錛岃€岄潪綾誨瀷 null銆傝繖鐐規綔鍦ㄧ殑娣鋒穯鏄負浜嗗悜涓嬪吋瀹廣€?/font>
Undefined 鏁版嵁綾誨瀷
濡備笅鎯呭喌浣胯繑鍥?undefined 鍊鹼細
- 瀵硅薄灞炴€т笉瀛樺湪錛?
- 澹版槑浜嗗彉閲忎絾浠庢湭璧嬪€箋€?
娉ㄦ剰涓嶈兘閫氳繃涓?undefined 鍋氭瘮杈冩潵嫻嬭瘯涓€涓彉閲忔槸鍚﹀瓨鍦紝铏界劧鍙互媯€鏌ュ畠鐨勭被鍨嬫槸鍚︿負鈥渦ndefined鈥濄€傚湪浠ヤ笅鐨勪唬鐮佽寖渚嬩腑錛屽亣璁劇▼搴忓憳鎯蟲祴璇曟槸鍚﹀凡緇忓０鏄庡彉閲?x 錛?/font>
//榪欑鏂規硶涓嶈搗浣滅敤if (x == undefined)//浣滄煇浜涙搷浣?//榪欎釜鏂規硶鍚屾牱涓嶈搗浣滅敤-蹇呴』媯€鏌?//瀛楃涓?code> "undefined"if (typeof(x) == undefined)//浣滄煇浜涙搷浣?//榪欎釜鏂規硶鏈夋晥if (typeof(x) == "undefined")//浣滄煇浜涙搷浣?/font>
鑰冭檻灝?undefined 鍊間笌null鍋氭瘮杈冦€?/font>
someObject.prop == null;
濡備笅鎯呭喌鏃訛紝姣旇緝鐨勭粨鏋滀負 true錛?
- 濡傛灉灞炴€?someObject.prop 鍖呭惈 null 鍊鹼紝
- 濡傛灉灞炴€?someObject.prop 涓嶅瓨鍦ㄣ€?
- 瑕佹鏌ヤ竴涓璞″睘鎬ф槸鍚﹀瓨鍦紝鍙互浣跨敤鏂扮殑 in 榪愮畻絎︼細
if ("prop" in someObject) // someObject鏈夊睘鎬?/font>'prop'
榪愮畻絎?/font>
JScript 鍏鋒湁鍏ㄨ寖鍥寸殑榪愮畻絎?鍖呮嫭綆楁湳銆侀€昏緫銆佷綅銆佽祴鍊間互鍙婂叾浠栨煇浜涜繍綆楃銆?/font>
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