Insert an element at a specified position in a JS array at a specific index_javascript tips

Many array-related tasks sound simple, but this is not always the case, and developers often do not need them. Recently I came across the need to insert an element into an existing array at a specific index. It sounds easy and common, but it takes a little time to research it.

// 原来的数组 
var array = ["one", "two", "four"]; 
// splice(position, numberOfItemsToRemove, item) 
// 拼接函数(索引位置, 要删除元素的数量, 元素) 
array.splice(2, 0, "three"); 

array; // 现在数组是这个样子 ["one", "two", "three", "four"]

If you are not averse to extending native JavaScript, you can add this method to the Array prototype:

Array.prototype.insert = function (index, item) { 
this.splice(index, 0, item); 
};

At this time, you can call it like this:

var nums = ["one", "two", "four"]; 
nums.insert(2, 'three'); // 注意数组索引, [0,1,2..] 
array // ["one", "two", "three", "four"]