6. Statements

for-in

用于遍历key不是symbol类型的对象

for (const propName in window) {
document.write(propName);
}

for-of

用于iterable的对象

for (const el of [2,4,6,8]) {
document.write(el);
}

label, break, continue

break跳出当前循环，continue跳出本次循环继续下一次循环

let num = 0;
outermost:
for (let i = 0; i < 10; i++) {
  for (let j = 0; j < 10; j++) {
    if (i == 5 && j == 5) {
      break outermost;  //用label指定要跳出的循环
      // continue outermost;   
    }
    num++;
  }
}
console.log(num); // 95

with(不推荐)

// location是对象
with(location) {
  let qs = search.substring(1);
  let hostName = hostname;
  let url = href;
}
// 等价于
let qs = location.search.substring(1);
let hostName = location.hostname;
let url = location.href;

switch

switch用的是===，不会发生类型转换

switch (i) {
  case 25:
    /* falls through */   // 不加break则执行下一行
  case 35:
    console.log("25 or 35");
    break;
  case 45:
    console.log("45");
    break;
  default:
    console.log("Other");
}