nairihar

const merge = require('webpack-merge');
const common = require('./webpack.common.js');

module.exports = merge(common, {
  mode: 'development',
  devServer: {
    contentBase: './dist'
  }
});

nairihar

const path = require('path');
const CleanWebpackPlugin = require('clean-webpack-plugin');
const HtmlWebpackPlugin = require('html-webpack-plugin');

module.exports = {
  entry: {
    app: './src/index.js'
  },
  module: {
    rules: [

nairihar

{
  "name": "react-application",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",

nairihar

const weakSet = new WeakSet();

const obj = {};

weakSet.add(obj);
weakSet.has(obj);
// true

weakSet.delete(obj);
// true

nairihar

const weakMap = new WeakMap();

let obj = {};

weakMap.set(obj, 11);
weakMap.get(obj);
// 11

console.log(weakMap);

nairihar

const weakMap = new WeakMap();

const obj = {};

weakMap.set(obj, 11);
weakMap.set(1,1);
// Uncaught TypeError: Invalid value used as weak map key

weakMap.get(obj);
// 11

nairihar

In some cases you won't have an access to modify the object.
So, what kind of cases they are?

nairihar

const weakMap = new WeakMap(); // be sure you using custom WeakMap not native

const obj = Object.freeze({ hello: true });

weakMap.set(obj, 12);

nairihar

const myMap = new Map();

const arr1 = [];
const arr2 = [];

myMap.set(arr1, 1);
myMap.set(arr2, 2);

console.log([...myMap]);
/*

nairihar

const obj = {};

const arr1 = [];
const arr2 = [];

obj[arr1] = 1;
obj[arr2] = 2;

console.log(obj);
// {"": 2}