Day14 要來學習怎麼複製資料

Q1

• 基本型別是 call by value ，所以不會更改到原始資料

        let age = 100;
        let age2 = age;
        age = 200;

Q2

• 字串也是基本型別

        let name = "Wes";
        let name2 = name;
        name = "wesley";

Q3

• 陣列是 call by reference，team 與 players 指向相同，所以會更動到原始的陣列

        const players: string[] = ["Wes", "Sarah", "Ryan", "Poppy"];
        const team: string[] = players;
        team[3] = "Lux";

Q4

• slice() 會回傳新的陣列，所以不會更動到原始資料

        const players: string[] = ["Wes", "Sarah", "Ryan", "Poppy"];
        const team2: string[] = players.slice();
        team2[3] = "Copy 1";

Q5

• 先建立空的陣列，再用 concat() 連接起來也可以複製陣列

        const players: string[] = ["Wes", "Sarah", "Ryan", "Poppy"];
        const team3: string[] = ([] as string[]).concat(players);
        team3[3] = "Copy 2";

Q6

• 展開運算子可以複製陣列

        const players: string[] = ["Wes", "Sarah", "Ryan", "Poppy"];
        const team4: string[] = [...players];
        team4[3] = "Copy 3";

Q7

• Array.from() 可以複製陣列

        const players: string[] = ["Wes", "Sarah", "Ryan", "Poppy"];
        const team5: string[] = Array.from(players);
        team5[3] = "Copy 4";

Q8

• 物件的複製可以用 Object.assign() 來建立新的物件，然後用來包裝原始資料與新的資料

        const person: Person = { name: "Wes Bos", age: 80 };
        const cap2: Person = Object.assign({}, person, { number: 99, age: 12 });

Q9

• 如果要複製很多層的資料可以使用 JSON.parse(JSON.stringify(data)

        const wes: Wes = {
          name: "Wes",
          age: 100,
          social: {
            twitter: "@wesbos",
            facebook: "wesbos.developer",
          },
        };
        const dev2: Wes = JSON.parse(JSON.stringify(wes));
        dev2.social.twitter = "@wesdev";

DEMO

https://codesandbox.io/p/devbox/day14-javascript-references-vs-copying-7gtntz