js【詳解】arr.splice() 數組拼接

arr.splice() 的含義

splice的中文釋義為“拼接”，arr.splice() 即剪切掉數組中一個連續的片段後，再拼接上一個新片段。

arr.splice() 的文法

let newArr = arr.splice(起始索引index, 删除的個數, 新增元素1, 新增元素2...)   // 傳回被删除元素組成的新數組
           

會改變原數組

第三個及之後的參數表示：向原數組中添加新的元素，這些元素将會自動插入到開始位置索引的前面。

若未指定删除的個數，則從起始索引index到數組最後一個元素全部删除

arr.splice() 的使用

// 範例1 —— 從第index為1的位置開始，删除之後的所有元素
let arr1 = ["a", "b", "c", "d", "e", "f"];
let result1 = arr1.splice(1); 

arr1：["a"]
result1：["b","c","d","e","f"]
           

//範例2 —— 删除最後兩個元素
let arr = ["a", "b", "c", "d", "e", "f"];
let result = arr.splice(-2); 

arr：["a","b","c","d"]
result：["e","f"]
           

//範例3 —— 從index為1的元素開始，一共删除三個元素
let arr = ["a", "b", "c", "d", "e", "f"];
let result = arr.splice(1, 3); 

arr：["a","e","f"]
result：["b","c","d"]
           

//範例4 —— 從index為1的元素開始，一共删除三個元素,并且在 index=1 的前面追加兩個元素
let arr = ["a", "b", "c", "d", "e", "f"];
let result = arr.splice(1, 3, "新增元素1", "新增元素2");

arr：["a","新增元素1","新增元素2","e","f"]
result：["b","c","d"]
           

//範例5 —— E6文法實作數組合并-将arr2合并到arr1
let arr1 = ["a", "b", "c"];
let arr2 = ["1", "2", "3"];

arr1.splice(0, 0, ...arr2);

arr1: [ '1', '2', '3', 'a', 'b', 'c' ]