一文搞懂 js 中的各种 for 循环的不同之处

一文搞懂 js 中的各种 for 循环的不同之处

See the Pen for...in vs for...of by xgqfrms
(@xgqfrms) on CodePen.

for

"use strict";

/**
 *
 * @author xgqfrms
 * @license MIT
 * @copyright xgqfrms
 * @created 2020-07-01
 * @modified
 *
 * @description for : var hoisting, break loop, support array-like loop
 * @augments
 * @example
 * @link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for
 *
 */

const log = console.log;

const arr = [1, 2, 3, 4];

const obj = {
  a: "A",
  b: "B",
  c: "C",
};

for (var index = 0; index < 3; index++) {
  log(`index`, index)
}
// index 0
// index 1
// index 2

log(`hoisting index`, index)
// hoisting index 3

for (let indexLet = 0; indexLet < 3; indexLet++) {
  log(`indexLet`, indexLet)
}
// indexLet 0
// indexLet 1
// indexLet 2

try {
  log(`not hoisting index`, indexLet);
  // ReferenceError: indexLet is not defined
} catch (error) {
  log(`js `)
}

for (let i = 0; i < arr.length; i++) {
  if (i === 3) {
    log(`