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 /// <reference path="http://tech.idv2.com/2008/01/09/javascript-variables-and-delete-operator/" />
/*
Óëc++²»Í¬£¬javascriptµÄdelete²»»áɾ³ýÊôÐÔËùÖ¸ÏòµÄ¶ÔÏó
“ɾ³ýÊôÐÔ¶ø²»ÊÇɾ³ý¶ÔÏó”ÕâÒ»µã£¬¿ÉÒÔͨ¹ýÒÔϵĴúÂëÀ´È·ÈÏ¡£
*/
var o = {};
var a = { x: 10 };
o.a = a;
delete o.a; // o.aÊôÐÔ±»É¾³ý
o.a; // undefined
a.x; // 10, ÒòΪ{ x: 10 } ¶ÔÏóÒÀÈ»±» a ÒýÓã¬ËùÒÔ²»»á±»»ØÊÕ
/*
ÊôÐÔdelete**½áÂÛ£ºdeleteɾ³ý¶ÔÏóʵÀýµÄÊôÐÔ Ö»¶Ô¶ÔÏóʵÀý²Ù×÷,²»»áÓ°Ïìµ½ËûµÄÀàÐͺÍÔ­ÐÍ
*/
function C() { this.x = 42; } //¹¹Ô캯Êý¡£
C.prototype.x = 12; //¸øoµÄÔ­ÐͶÔÏóÌí¼ÓÊôÐÔx£¬ËùÒÔ²»»á±»delete¡£
var o = new C(), d = new C();
alert(o.prototype); //ÏÔʾundefined£¬ÒòΪÆäʵֻÓк¯Êý²ÅÓÐprototypeÊôÐÔ
//alert(C.prototype.isPrototypeOf(o));
alert(o.x); // 42, ¹¹Ô캯ÊýÖж¨ÒåµÄo.x
delete o.x; // deleteɾ³ýÊôÐÔ Ö»¶Ô¶ÔÏóʵÀý²Ù×÷,²»»áÓ°Ïìµ½ËûµÄÔ­ÐÍ
alert(o.x); // 12 ÔÚ×ÔÉíÉÏÕÒ²»µ½x£¬¾Í»á²éÕÒÔ­ÐÍÁ´¡£
alert(d.x); // 42 ÒòΪֻɾÁËʵÀýoµÄxÊôÐÔ£¬²¢Ã»É¾ÊµÀýdµÄxÊôÐÔ£¬ÕâÀï²»»áÏÔʾundefined
/*
²âÊÔ±äÁ¿delete**½áÂÛ£ºÍ¨¹ývarÉùÃ÷µÄ±äÁ¿ºÍͨ¹ýfunctionÉùÃ÷µÄº¯ÊýÓµÓÐDontDeleteÌØÐÔ£¬
ÎÞ·¨±»É¾³ý¡£Èç¹ûÄãÔø¾­ÓñհüÄ£Äâ¹ýÀàµÄ˽ÓÐÊôÐÔ¡¢·½·¨£¬ÄÇÒ²¿ÉÒÔÕâÑùÀí½â£¬Í¨¹ývarºÍ
functionÉùÃ÷µÄ±äÁ¿ºÍÓÐÃûº¯Êý£¬¶¼ÊÇ¿ÉÒÔ¿´×öÀàµÄ˽ÓеijÉÔ±£¬Ë½ÓгÉÔ±¾ßÓÐDontDeleteÌØÐÔ¡£
*/
var a = 1;
delete a;
b = 2; //ûÓÐÓÃvar£¬¿ÉÒÔÀí½âĬÈÏΪ¹«ÓеÄÊôÐÔ£¬¿ÉÒÔ±»É¾³ý
delete b;
alert(typeof b); //undefinded£¬±»É¾ÁË
function foo() {//È«¾Ö¶ÔÏóµÄ˽Óз½·¨
return 42;
}
delete foo;
alert(foo()); // 42
function foo1() {
var local = 36;
delete local; // ɾ³ýlocal£¬ºÜÏÔÈ»localÊÇ˽ÓгÉÔ±£¬Ã»É¾µô
alert(local);
}
foo1();
/*
evalºÍdelete**½áÂÛ£ºeval±È½ÏÌØÊ⣬²Î¿¼
http://tech.idv2.com/2008/01/09/javascript-variables-and-delete-operator/#content_2_4
*/
eval("var x = 36;"); //×¢Ò⣺evalÊÜ×÷ÓÃÓòÓ°Ï죬¸ü¶à²Î¿¼htt


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