Closure
其他語言也有closure
可提供類似其他語言的static function-使用static data, 以及跟module pattern結合提供內部private function的空間
Closure使用到的變數的lifetime只要還有人指到這個closure function時,這些變數就會隨著存活.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures A closure is a function having access to the parent scope, even after the parent function has closed.
上述link有提到跟 closure相關的 lexical scoping:
the code and see that this works. This is an example of lexical scoping: in JavaScript, the scope of a variable is defined by its location within the source code (it is apparent lexically) and nested functions have access to variables declared in their outer scope.
上述link裡的example, 放在online JB Bin上:http://jsbin.com/wurihum/edit?html,js,output 其code:
var add = (function () {
var counter = 0;
debugger;
return function () {
counter = counter +1;
debugger; //用chrome dev tool看, 會看到closure scope
return counter;
};
})();
add();
debugger;
add();
debugger;
add();
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