JavaScript - slice()、splice()、split() 詳細介紹

目標對象

• slice(): Array 及 String
• splice(): Array
• split(): String

功能說明

slice()

複製開始與結束點（結束點不算）中的內容

arr.slice()
arr.slice(begin) /* 含 end 項 */
arr.slice(begin, end) /* 包含 begin項 但不包含 end 項 */

begin 為開始的索引值，若為 負數 則從後面算起。
end 為結束的索引值，若無填寫則直接預設為最後一項。
以下是參考用法:

const game = ['PS4', 'Xbox', 'Switch', 'N3DS'];
const game_1 = game.slice(1);
const game_2 = game.slice(1, 2);
const game_3 = game.slice(-3);

// game contains ['PS4', 'Xbox', 'Switch', 'N3DS']
// game_1 contains ['Xbox', 'Switch', 'N3DS']
// game_2 contains ['Xbox', 'Switch']
// game_3 contains ['Xbox', 'Switch', 'N3DS']

const game_string = 'PS4XboxSwitch';
const game_string_1 = game_string.slice(1);
const game_string_2 = game_string.slice(1, 2);
const game_string_3 = game_string.slice(-3);

// game_string_1 contains S4XboxSwitch
// game_string_2 contains S
// game_string_3 contains tch

splice()

將原 Array 置換項目，並回傳被置換的項目。

array.splice(start)
array.splice(start, deleteCount)
array.splice(start, deleteCount, item1, item2, ...)

start 置換項目的位置，負數代表從後方算起。
deleteCount 置換的個數，如為 0 則不會置換。
item 添加的新項目。
以下是參考用法:

  var game_1 = ['PS4', 'Xbox', 'Switch', 'N3DS'];
  var game_removed_1 = game_1.splice(2, 1, 'PC');

  // game_1 = ['PS4', 'Xbox', 'PC', 'N3DS'];
  // game_removed_1 is ['Switch']

  var game_2 = ['PS4', 'Xbox', 'Switch', 'N3DS'];
  var game_removed_2 = game_2.splice(-2, 2, 'PC');

  // game_2 = ['PS4', 'Xbox', 'PC'];
  // game_removed_2 is ['Switch', 'N3DS']

  var game_3 = ['PS4', 'Xbox', 'Switch', 'N3DS'];
  var game_removed_3 = game_3.splice(2, 1);

  // game_3 = ['PS4', 'Xbox', 'N3DS'];
  // game_removed_3 is ['Switch']
  ``` 

### split()
  將 `String` 依照規則區分，並放入 `Array` 內
  ``` JavaScript
  stringObject.split(separator,howmany)

separator 自訂字串符或正則表達式，從該參數指定的地方分割 String。
howmany 返回值的最大長度，超過該長度則不顯示。
以下是參考用法:

var str = "How are you ?"
var splits_1 = str.split(" ");
var splits_2 = str.split("");
var splits_3 = str.split(" ",3);

//splits1 contains ["How", "are", "you", "?"]
//splits2 contains ["H", "o", "w", " ", "a", "r", "e", " ", "y", "o", "u", " ", "?"]
//splits3 contains ["How", "are", "you"]

參考資料

Array.prototype.slice()
Array.prototype.splice()
String.prototype.split()