Proxy

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definition

Proxy is a new API in ES6, which is used to redefine some basic operation of Object.

usage

Proxy(target, handlers), target is the target object while handlers is an object whose properties are functions that define the user's behaviors when performing operations. Those operations are also called traps.

let obj = new Proxy({}, {
  get(obj, prop) {
    return (obj[prop]) ? obj[prop] : 'undefined property';
  },
  set(obj, prop, val) {
    if (prop in obj) {
      throw 'duplicate definition';
    } else {
      obj[prop] = val;
      return true;
    }
  }
});
console.log(obj.a); // undefined property
obj.a = 100;
console.log(obj.a); // 100
obj.a = 1000; // throw error