数据绑定

defineProperty

<input id="input" type="text" />
<div id="text"></div>

let input = document.getElementById("input");
let text = document.getElementById("text");
let data = { value: "" };
Object.defineProperty(data, "value", {
  set: function(val) {
    text.innerHTML = val;
    input.value = val;
  },
  get: function() {
    return input.value;
  }
});
input.onkeyup = function(e) {
  data.value = e.target.value;
};

Proxy

Proxy 是 ES6 中新增的功能，可以用来自定义对象中的操作

let p = new Proxy(target, handler);
// `target` 代表需要添加代理的对象
// `handler` 用来自定义对象中的操作

可以很方便的使用 Proxy 来实现一个数据绑定和监听

let onWatch = (obj, setBind, getLogger) => {
  let handler = {
    get(target, property, receiver) {
      getLogger(target, property)
      return Reflect.get(target, property, receiver);
    },
    set(target, property, value, receiver) {
      setBind(value);
      return Reflect.set(target, property, value);
    }
  };
  return new Proxy(obj, handler);
};

let obj = { a: 1 }
let value
let p = onWatch(obj, (v) => {
  value = v
}, (target, property) => {
  console.log(`Get '${property}' = ${target[property]}`);
})
p.a = 2 // bind `value` to `2`
p.a // -> Get 'a' = 2