获取请求的子对象的名称 javascript [英] Get the name of the requested subobject javascript

问题描述

如果我有一个带有匿名函数的对象，我怎么知道正在请求什么子对象以便我可以返回一个值?

If I have an object with an anonymous function inside how do I know what subobject is being requested so that I can return a value?

var obj = function(a) {
    switch (a) {
        case 'subprop1': return 'subval1';
        case 'subprop2': return 'subval2';
        case 'subprop3': return 'subval3';
        default: return 'defaultval'; 
    }
}

所以如果我打电话:

obj.subprop1

我应该得到:

subval1

推荐答案

除非您的环境支持 Proxy.

This is not really possible with plain objects unless your environment supports Proxy.

在这种情况下，它会很容易(尚未测试):

In this case it would be quite easy (haven't tested):

var obj = function(a) {
    switch (a) {
        case 'subprop1': return 'subval1';
        case 'subprop2': return 'subval2';
        case 'subprop3': return 'subval3';
        default: return 'defaultval'; 
    }
};

var objProxy = new Proxy(obj, {
    get: function (target, name) { return target(name); }
});

objProxy.subprop1; //should return subval1
objProxy.nonExisting; //shoud return defaultval

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