函数的扩展

// demo1
// ES5
function log(x, y) {
  y = y || 'World';
  console.log(x, y);
}

log('Hello');
log('Hello', 'China');
log('Hello', '');

// ES6
function log(x, y = 'World') {
  console.log(x, y);
}
log('Hello');
log('Hello', 'China');
log('Hello', false);

// 实例1
function Point(x = 0, y = 0) {
  this.x = x;
  this.y = y;
}

var p = new Point();
console.log(p);

// 与解构赋值默认值结合使用
function foo({ x, y = 5 }) {
  console.log(x, y);
}

foo({});
foo({ x: 1 });
foo({ x: 1, y: 2 });
foo();

// demo1
function add(...values) {
  let sum = 0;
  for (var val of values) {
    sum += val;
  }
  return sum;
}

add(2, 3, 4, 5);

// demo2 rest代替arguments
// 数组排序 arguments变量的写法
function sortNumbers1() {
  return Array.prototype.slice.call(arguments).sort();
}

// 数组排序 rest参数的写法
const sortNumbers2 = (...numbers) => numbers.sort();

// demo3 替代数组的apply方法
function f(x, y, z) {
  //...
}
var args = [0, 1, 2];
f.apply(null, args);

//ES6的写法
function f1(x, y, z) {
  //...
}
var args1 = [1, 2, 3];
f1(...args1);

// demo4 数组合并
var arr1 = [0, 2, 4];
var arr2 = [1, 3, 4];
Array.prototype.push.apply(arr1, arr2);

// ES6的写法
var arr3 = [9, 8, 7];
var arr4 = [6, 5, 4];
arr3.push(...arr4);

const func = () => {
  console.log('test');
};

setTimeout(() => {}, 1000);