本文通過舉例,由淺入深的講解了解決js函數閉包內存洩露問題的辦法,分享給大家供大家參考,具體內容如下
原始代碼:
function Cars(){ this.name = "Benz"; this.color = ["white","black"]; } Cars.prototype.sayColor = function(){ var outer = this; return function(){ return outer.color }; }; var instance = new Cars(); console.log(instance.sayColor()())
優化後的代碼:
function Cars(){ this.name = "Benz"; this.color = ["white","black"]; } Cars.prototype.sayColor = function(){ var outerColor = this.color; //保存一個副本到變量中 return function(){ return outerColor; //應用這個副本 }; outColor = null; //釋放內存 }; var instance = new Cars(); console.log(instance.sayColor()())
稍微復雜一點的例子:
function inheritPrototype(subType,superType){ var prototype = Object(superType.prototype); prototype.constructor = subType; subType.prototype = prototype; } function Cars(){ this.name = "Benz"; this.color = ["white","black"]; } Cars.prototype.sayColor = function(){ var outer = this; return function(){ return outer.color; }; }; function Car(){ Cars.call(this); this.number = [321,32]; } inheritPrototype(Car,Cars); Car.prototype.sayNumber = function(){ var outer = this; return function(){ return function(){ return outer.number[outer.number.length - 1]; } }; }; var instance = new Car(); console.log(instance.sayNumber()()());
首先,該例子組合使用了構造函數模式和原型模式創建Cars 對象,並用了寄生組合式繼承模式來創建Car 對象並從Cars 對象獲得屬性和方法的繼承;
其次,建立一個名為instance 的Car 對象的實例;instance 實例包含了sayColor 和sayNumber 兩種方法;
最後,兩種方法中,前者使用了一個閉包,後者使用了兩個閉包,並對其this 進行修改使其能夠訪問到this.color 和this.number。
這裡存在內存洩露問題,優化後的代碼如下:
function inheritPrototype(subType,superType){ var prototype = Object(superType.prototype); prototype.constructor = subType; subType.prototype = prototype; } function Cars(){ this.name = "Benz"; this.color = ["white","black"]; } Cars.prototype.sayColor = function(){ var outerColor = this.color; //這裡 return function(){ return outerColor; //這裡 }; this = null; //這裡 }; function Car(){ Cars.call(this); this.number = [321,32]; } inheritPrototype(Car,Cars); Car.prototype.sayNumber = function(){ var outerNumber = this.number; //這裡 return function(){ return function(){ return outerNumber[outerNumber.length - 1]; //這裡 } }; this = null; //這裡 }; var instance = new Car(); console.log(instance.sayNumber()()());
以上就是為大家分享的解決方法,希望對大家的學習有所幫助。