jsä¸æ5ç§æ°æ®ç±»åï¼UndefinedãNullãBooleanãNumberåStringã
è¿æä¸ç§å¤æçæ°æ®ç±»åObjectï¼Objectæ¬è´¨æ¯ä¸ç»æ åºçåå¼å¯¹ç»æçã
Undefinedç±»ååªæä¸ä¸ªå¼ï¼å³undefinedï¼ä½¿ç¨var声æåéï¼ä½æ¯æªå¯¹åå§åçï¼è¿ä¸ªåéå°±æ¯Undefinedç±»åçï¼ä¾åï¼
var
i;
alert(i == undefined);//true
var i;ä¸var i =
undefined;è¿ä¸¤å¥æ¯çä»·çã
å
å«Undefinedå¼çåéåæªå®ä¹çåéæ¯ä¸ä¸æ ·çã
Nullç±»åä¹åªæä¸ä¸ªå¼ï¼null.null表示ä¸ä¸ªç©ºå¯¹è±¡çæéã
Booleanç±»åï¼åªæ两个åé¢étrueåfalseãä½æ¯jsä¸å¤æçåéé½å¯ä»¥ä½¿ç¨Boolean()å½æ°è½¬æ¢æä¸ä¸ªBooleanç±»åçå¼ã
Numberç±»åï¼æ´æ°åæµ®ç¹æ°ãNaNï¼Not
a Numberãè¿ä¸ªæ°å¼ç¨äºæ¬æ¥è¦è¿åä¸ä¸ªæ°å¼ï¼ä½æ¯å´æªè½æ¾åä¸ä¸ªæ°å¼çæ
åµï¼ä»¥é²æ¢æ¥éãä¾å¦ï¼1/0
è¿åçå°±æ¯NaNãNaNçç¹ç¹ï¼1ãä»»ä½æ¶åNaNçæä½é½ä¼è¿åNaNã2ãNaN对任ä½å¼é½ä¸ç¸çï¼å
æ¬èªå·±NaNæ¬èº«ã
é对NaNç¹æ§ï¼JSå
ç½®äºisNaN()å½æ°ï¼æ¥ç¡®å®æ°å¼æ¯ä¸æ¯NaNç±»åã
Stringç±»åï¼ç¥
typeofæä½ç¬¦ï¼å¯¹ä¸ä¸ªåéè¿è¡æ¨æåéçç±»åï¼å¯è½è¿å以ä¸å符串ï¼
"undefined"
å¦æè¿ä¸ªå¼ï¼æªå®ä¹æè
为åå§å
"boolean" å¸å°å¼
"string" å符串
"number" æ°å¼
"object"
对象
"function" å½æ°
ç¨æ³ï¼typeof 95; æè
typeof(95); ä¼è¿å"number".
温馨提示:答案为网友推荐,仅供参考