在对象上定义getter方法--javascript

Question

我想在对象上定义 getter 方法，这样当我访问属性时，getter方法会触发

object.someProperty // this fires object.get(name) where name is someProperty

这是一个说明我的想法的例子

file：data.js

import setting from 'setting';

const data = {
    a : {
        foo : 1 ,
        bar : 2
    } ,
    b : {
        foo : 3 ,
        bar : 4
    }
}

//DEFINE GETTER
//something like this
data.DEFINE_GETTER(function(property)
{
    if(setting.type === 'a')
        return data['a'][property];
    else
        return data['b'][property];
})

export default data;

file：test.js

import data from 'data';
import setting from 'setting';

setting.type = 'a';
console.log(data.foo)   //should be 1
console.log(data.bar)   //should be 2

setting.type = 'b';
console.log(data.foo)   //should be 3
console.log(data.bar)   //should be 4

Answer 1

您可以定义getter

Object.defineProperty(data, 'foo', {
  get: function() { return this[setting.type].foo }
});
Object.defineProperty(data, 'bar', {
  get: function() { return this[setting.type].bar }
});

修改

您可以将defineProperty重构为迭代data

中所有不同键的方法

function defineDataProp( obj, setting )
{
  Object.keys(Object.values( obj )[0]).forEach( function(key){
      Object.defineProperty(obj, key, {
         get: function() { return this[setting.type][ key ] }
      });
  })
}

<强>演示

＆＃13;

＆＃13;

const data = {
    a : { foo : 1 , bar : 2 } ,
    b : { foo : 3 , bar : 4 }
};

var setting = { "type" : "a" };
defineDataProp( data, setting );

setting.type = 'a';
console.log(data.foo,data.bar)   

setting.type = 'b';
console.log(data.foo,data.bar)

function defineDataProp( obj, setting )
{
  Object.keys(Object.values( obj )[0]).forEach( function(key){
      Object.defineProperty(obj, key, {
         get: function() { return this[setting.type][ key ] }
      });
  })
}

＆＃13;

＆＃13;

＆＃13;

Answer 2

使用代理处理程序

let handler = {
    get(target, propKey, receiver) {
        console.log('get ' + propKey);
        if(setting.type === 'a')
        return data['a'][propKey];
    else
        return data['b'][propKey];
    }
};
let proxyData = new Proxy(data, handler);
// now you can call
proxyData.foo
proxyData.bar