解决js函数闭包内存泄露问题的办法
本文通过举例,由浅入深的讲解了解决js函数闭包内存泄露问题的办法,分享给大家供大家参考,具体内容如下
原始代码:
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()())
优化后的代码:
function Cars(){
this.name = "Benz";
this.color = ["white","black"];
}
Cars.prototype.sayColor = function(){
var outerColor = this.color; //保存一个副本到变量中
return function(){
return outerColor; //应用这个副本
};
outColor = null; //释放内存
};
var instance = new Cars();
console.log(instance.sayColor()())
稍微复杂一点的例子:
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,该例子组合使用了构造函数模式和原型模式创建Cars 对象,并用了寄生组合式继承模式来创建Car 对象并从Cars 对象获得属性和方法的继承;
其次,建立一个名为instance 的Car 对象的实例;instance 实例包含了sayColor 和sayNumber 两种方法;
最后,两种方法中,前者使用了一个闭包,后者使用了两个闭包,并对其this 进行修改使其能够访问到this.color 和this.number。
这里存在内存泄露问题,优化后的代码如下:
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; //这里
return function(){
return outerColor; //这里
};
this = null; //这里
};
function Car(){
Cars.call(this);
this.number = [321,32];
}
inheritPrototype(Car,Cars);
Car.prototype.sayNumber = function(){
var outerNumber = this.number; //这里
return function(){
return function(){
return outerNumber[outerNumber.length - 1]; //这里
}
};
this = null; //这里
};
var instance = new Car();
console.log(instance.sayNumber()()());
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