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()()());`
|
