Obj/Array References Day 14 of 30.

2023-03-03 09:48:37 -08:00 · 2023-03-03 09:48:37 -08:00 · 87880aa939
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 <!DOCTYPE html>
 <html lang="en">
 <head>
  <meta charset="UTF-8">
  <title>JS Reference VS Copy</title>
  <link rel="icon" href="https://fav.farm/🔥" />
 </head>
 <body>
  <script>
    // start with strings, numbers and booleans
    let age = 100;
    let age2 = age;
    console.log(age, age2);
    age = 200;
    console.log(age, age2);
    let name = 'cool';
    let name2 = name;
    console.log(name, name2);
    name = 'zero';
    console.log(name, name2)
    // Let's say we have an array
    const players = ['Wes', 'Sarah', 'Ryan', 'Poppy'];
    // and we want to make a copy of it.
    const team = players;
    console.log(players, team);
    // You might think we can just do something like this:
    team[3] = 'Lux';
    // however what happens when we update that array?
    // now here is the problem!
    // oh no - we have edited the original array too!
    // Why? It's because that is an array reference, not an array copy. They both point to the same array!
    // So, how do we fix this? We take a copy instead!
    const team2 = players.slice();
    // one way
    // or create a new array and concat the old one in
    const team3 = [].concat(players);
    // or use the new ES6 Spread
    const team4 = [...players];
    team4[3] = 'Sphinx'
    console.log(team4);
    const team5 = Array.from(players);
    // now when we update it, the original one isn't changed
    // The same thing goes for objects, let's say we have a person object
    // with Objects
    const person = {
      name: 'Wes Bos',
      age: 80
    };
    // and think we make a copy:
    const captain = person;
    captain.number = 99;
    // how do we take a copy instead?
    const cap2 = Object.assign({}, person, { number: 99 });
    console.log(cap2);
    // We will hopefully soon see the object ...spread
    const cap3 = {...person};
    // Things to note - this is only 1 level deep - both for Arrays and Objects. lodash has a cloneDeep method, but you should think twice before using it.
    const worlddrknss = {
      name: 'Charles',
      age: 100,
      social: {
        twitter: '@WorldDrknss',
        facebook: 'skynetinctech'
      }
    }
    console.log(worlddrknss);
    const dev = Object.assign({}, worlddrknss);
    const dev2 = JSON.parse(JSON.stringify(worlddrknss));
  </script>
 </body>
 </html>