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在Javascript是可以使用“delete”來手動刪除變數，通過這樣的方法讓GC(Garbage collection)來回收記憶體，但在JS中並不是所有的變數都可以被刪除的。
1、var 聲明的 全域變數“a” 在使用 “delete a” 後 輸出值依然為 “1”。
2、未使用var 聲明的全域變數“b” 成為了 “window”的屬性，在使用 “delete b” 後 輸出 報錯 “b is not defined”。
3、在對象或者 構造器中的 變數，在使用 “delete” 後輸出 “undefined”。
<!DOCTYPE html><html> <head> <meta charset="utf-8"> <title>javascript 釋放變數</title> </head> <body> <script type="text/javascript"> var a = 1; b = 2; function asda(){ var g = 5; delete g; console.log(g); } var function_name = function (argument) { this.c = 3; } var d = new function_name(); var e = {"f" : 4}; delete a; delete b; // delete window.b; delete d.c; delete e.f; asda(); // 5 console.log(a); // 1 console.log(b); // Uncaught ReferenceError： b is not defined console.log(d.c); // undefined console.log(e.f); // undefined </script> </body></html>Start building with 50+ products and up to 12 months usage for Elastic Compute Service
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