JavaScript null vs undefined

JavaScript null vs undefined

1. null 变量已声明，但给变量分配空值;

2. undefined 变量已声明，但尚未分配任何值;

"use strict";

/**
 *
 * @author xgqfrms
 * @license MIT
 * @copyright xgqfrms
 * @created 2020-07-23
 * @modified
 *
 * @description null vs undefined
 * @difficulty Easy
 * @complexity O(n)
 * @augments
 * @example
 * @link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/null
 * @link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/undefined
 * @solutions
 *
 */

const log = console.log;

// null 变量已声明，但给变量分配空值;
// undefined 变量已声明，但尚未分配任何值;

const obj = { k1: undefined, k2: null, };
// {k1: undefined, k2: null}

const {
  k1,
  k2,
} = obj;

k1;
// undefined
k2;
// null

log(`k1 =`, k1)
log(`k2 =`, k2)

// k1 = undefined
// k2 = null

refs

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