js 奇技淫巧

1. 初始化一个可伸缩长度的数组：

let len = 5
let arr = Array(len).fill(null).map((v, i) => String.fromCharCode(65 + i));
let arr = Array.apply(null, {length: len}).map((v, i) => String.fromCharCode(65 + i));

console.log(arr); //[ 'A', 'B', 'C', 'D', 'E' ]

2. 对象属性值监听

let data = {
  title: 'hello world!'
};

function definePropertyData(obj, prop, value) {
  Object.defineProperty(obj, prop, {
    get: function () {
      console.log(111)
      return value;
    },
    set: function (newValue) {
      value = newValue;
    },
  });
}

definePropertyData(data, 'title', data.title);

console.log(data.title) // 111 hello world!
data.title = 38;
console.log(data.title) // 111 38