A brief discussion on the add/delete operation of array Array in javascript

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javascript Array Array (list) Add/Delete

unshift: Add parameters to the beginning of the original array and return the length of the array

pop: Delete the last item of the original array and return the value of the deleted element; if the array is empty Then return undefined

push: add the parameters to the end of the original array, and return the length of the array

concat: return a new array, which is composed of adding the parameters to the original array

splice(start,deleteCount,val1,val2,…): Delete deleteCount items from the start position, and insert val1, val2,… from this position

reverse: Reverse the array

sort(orderfunction): Sort the array according to the specified parameters

slice(start,end): Return a new array composed of items from the specified start index to the end index in the original array

Details:

1. Creation of array

var arrayObj = new Array();　//创建一个数组
var arrayObj = new Array([size]);　//创建一个数组并指定长度，注意不是上限，是长度
var arrayObj = new Array([element0[, element1[, …[, elementN]]]]);　//创建一个数组并赋值

It should be noted that although the second The method creates an array with a specified length, but in fact the array is variable-length in all cases. That is to say, even if the length is specified as 5, elements can still be stored outside the specified length. Note: the length will change accordingly. .

2. Accessing array elements

var testGetArrValue=arrayObj[1]; //获取数组的元素值
 arrayObj[1]= “这是新值”; //给数组元素赋予新的值

3. Adding array elements

arrayObj. push([item1 [item2 [… [itemN ]]]]);// 将一个或多个新元素添加到数组结尾，并返回数组新长度
arrayObj.unshift([item1 [item2 [… [itemN ]]]]);// 将一个或多个新元素添加到数组开始，数组中的元素自动后移，返回数组新长度
arrayObj.splice(insertPos,0,[item1[, item2[, … [,itemN]]]]);//将一个或多个新元素插入到数组的指定位置，插入位置的元素自动后移，返回”“。

4. Deletion of array elements

arrayObj.pop(); //移除最后一个元素并返回该元素值
arrayObj.shift(); //移除最前一个元素并返回该元素值，数组中元素自动前移
arrayObj.splice(deletePos,deleteCount); //删除从指定位置deletePos开始的指定数量deleteCount的元素，数组形式返回所移除的元素

5. Interception and merging of arrays

arrayObj.slice(start, [end]); //以数组的形式返回数组的一部分，注意不包括 end 对应的元素，如果省略 end 将复制 start 之后的所有元素
arrayObj.concat([item1[, item2[, … [,itemN]]]]); //将多个数组（也可以是字符串，或者是数组和字符串的混合）连接为一个数组，返回连接好的新的数组

6. Copy of array

arrayObj.slice(0); //返回数组的拷贝数组，注意是一个新的数组，不是指向
arrayObj.concat(); //返回数组的拷贝数组，注意是一个新的数组，不是指向

7. Sorting of array elements

arrayObj.reverse(); //反转元素（最前的排到最后、最后的排到最前），返回数组地址
arrayObj.sort(); //对数组元素排序，返回数组地址

8. Sorting of array elements Stringification

arrayObj.join(separator); //返回字符串，这个字符串将数组的每一个元素值连接在一起，中间用 separator 隔开。

toLocaleString, toString, valueOf: can be regarded as special usage of join, not commonly used

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