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1. ת»»º¯Êý
jsÌṩÁËparseInt()ºÍparseFloat()Á½¸öת»»º¯Êý¡£Ç°Õß°Ñֵת»»³ÉÕûÊý£¬ºóÕß°Ñֵת»»³É¸¡µãÊý¡£Ö»ÓжÔStringÀàÐ͵÷ÓÃÕâЩ·½·¨£¬ÕâÁ½¸öº¯Êý²ÅÄÜÕýÈ·ÔËÐУ»¶ÔÆäËûÀàÐÍ·µ»ØµÄ¶¼ÊÇNaN(Not a Number)¡£
ÔÚÅжÏ×Ö·û´®ÊÇ·ñÊÇÊý×Öֵǰ£¬parseInt()ºÍparseFloat()¶¼»á×Ðϸ·ÖÎö¸Ã×Ö·û´®¡£parseInt()·½·¨Ê×ÏȲ鿴λÖÃ0´¦µÄ×Ö·û£¬ÅжÏËüÊÇ·ñÊǸöÓÐЧÊý×Ö£»Èç¹û²»ÊÇ£¬¸Ã·½·¨½«·µ»ØNaN£¬²»ÔÙ¼ÌÐøÖ´ÐÐÆäËû²Ù×÷¡£µ«Èç¹û¸Ã×Ö·ûÊÇÓÐЧÊý×Ö£¬¸Ã·½·¨½«²é¿´Î»ÖÃ1´¦µÄ×Ö·û£¬½øÐÐͬÑùµÄ²âÊÔ¡£ÕâÒ»¹ý³Ì½«³ÖÐøµ½·¢ÏÖ·ÇÓÐЧÊý×ÖµÄ×Ö·ûΪֹ£¬´ËʱparseInt()½«°Ñ¸Ã×Ö·û֮ǰµÄ×Ö·û´®×ª»»³ÉÊý×Ö¡£
ÀýÈ磬Èç¹ûÒª°Ñ×Ö·û´® "1234blue "ת»»³ÉÕûÊý£¬ÄÇôparseInt()½«·µ»Ø1234£¬ÒòΪµ±Ëü¼ì²âµ½×Ö·ûbʱ£¬¾Í»áÍ£Ö¹¼ì²â¹ý³Ì¡£×Ö·û´®Öаüº¬µÄÊý×Ö×ÖÃæÁ¿»á±»Õýȷת»»ÎªÊý×Ö£¬Òò´Ë×Ö·û´® "0xA "»á±»Õýȷת»»ÎªÊý×Ö10¡£²»¹ý£¬×Ö·û´® "22.5 "½«±»×ª»»³É22£¬ÒòΪ¶ÔÓÚÕûÊýÀ´Ëµ£¬Ð¡ÊýµãÊÇÎÞЧ×Ö·û¡£Ò»Ð©Ê¾ÀýÈçÏ£º
parseInt("1234blue");   //returns   1234
parseInt("0xA");   //returns   10
parseInt("22.5");   //returns   22
parseInt("blue");   //returns   NaN
parseInt()·½·¨»¹Óлùģʽ£¬¿ÉÒ԰Ѷþ½øÖÆ¡¢°Ë½øÖÆ¡¢Ê®Áù½øÖÆ»òÆäËûÈκνøÖƵÄ×Ö·û´®×ª»»³ÉÕûÊý¡£»ùÊÇÓÉparseInt()·½·¨µÄµÚ¶þ¸ö²ÎÊýÖ¸¶¨µÄ£¬ËùÒÔÒª½âÎöÊ®Áù½øÖƵÄÖµ£¬ÐèÈçϵ÷ÓÃparseInt()·½·¨£º
parseInt("AF",   16);   //returns   175
µ±È»£¬¶Ô¶þ½øÖÆ¡¢°Ë½øÖÆ£¬ÉõÖÁÊ®½øÖÆ£¨Ä¬ÈÏģʽ£©£¬¶¼¿ÉÒÔÕâÑùµ÷ÓÃparseInt()·½·¨£º
parseInt("10",   2);   //returns   2
parseInt("10",   8);   //returns   8
parseInt("10",   10);   //returns   10
Èç¹ûÊ®½øÖÆÊý°üº¬Ç°µ¼0£¬ÄÇô×îºÃ²ÉÓûùÊý10£¬ÕâÑù²Å²»»áÒâÍâµØµÃµ½°Ë½øÖƵÄÖµ¡£ÀýÈ磺
parseInt("010");   //returns   8
parseInt("010",   8);   //returns   8
parseInt("010",   10);   //returns   10
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    When web pages or applications begin to feel slow, analyzing assets as they come over the wire and profiling scripts while they are running allows you to focus your optimization efforts where they are needed most.
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