从子类访问javascript父类属性 [英] access javascript parent class properties from subclass

问题描述

大家好我在javascript中有一个关于obj的问题
如何访问父类属性

hi guys I had a question about obj in javascript how can I access parent class properties

function randomObj() // for example button obj
{
    this.text = "this is obj";
}

function parentClass()
{
    this.name = "parent";
    this.subObj;
}

parentClass.prototype.generate = function()
{
    this.subObj = new randomObj();
    this.subObj.changeParentClassName = function() // button obj wants to change name
    {
        this.name = "not parent";
    }
}

var sampleObj = new parentClass();
sampleObj.generate();
sampleObj.subObj.changeParentClassName (); // does not works

似乎'changeParentClassName'中的'this'是subObj，我怎样才能访问parentclass.name？
任何人都可以帮忙？

it seems 'this' in 'changeParentClassName' is subObj, how can I access parentclass.name ? anyone can help ??

推荐答案

JavaScript的此将调用函数时，它是。左侧的对象。在这种情况下，subObj不是parentObj，因此您在subObj上设置 name 。你有2个选项，你可以把这个放在 generate 里面的另一个变量中，这样它就不会被JavaScript取代此逻辑。类似于：

JavaScript's this will be the object to the left of the . when calling the function. In this case, it is the subObj not the parentObj so you are setting name on subObj. You have 2 options, you can put this in a different variable inside generate so it doesn't get replaced by JavaScript's this logic. Something like:

var parentObj = this;
this.subObj.changeParentClassName = function() // button obj wants to change name
{
    parentObj.name = "not parent";
};

或者您可以使用bind（）创建一个具有这个绑定到一个已知对象（在本例中是你的父对象）类似于：

Or you can use the bind() to create a new function that will have this bound to a known object (in this case your parent object) Something like:

this.subObj.changeParentClassName = (function() // button obj wants to change name
{
    this.name = "not parent";
}).bind(this); // bind the 'this' inside the changeParentClassName to the 'this' inside generate

签出函数bind（）获取有关绑定和交互式示例的更多信息。

Check out Function bind() for more info on bind and interactive examples.

注意，如果您要定位最新版本的Javascript（ECMAScript 6或更高版本），则可以使用 => 函数，该函数不会更改与声明范围相比，此的值。所以你可以使用：

Note, if you are targeting a recent version of Javascript (ECMAScript 6 or later), you can use a => function which does not change the value of this compared to the declaring scope. So you could use:

this.subObj.changeParentClassName = () => // button obj wants to change name
{
    this.name = "not parent";
};

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