A brief discussion on the usage of js arrays and splice

First add a splice function:

splice: The function of this method is to delete an element from the array

array.splice(index,count,value....);

index: Indicates which subscript to start from,

count: Indicates the number of deleted elements

value: Represents added elements

example:

1.var array = new Array(1,2,3,4,5,6);

array.splice(0,1,2)

result: 2,2,3,4,5

2.var array = new Array(1,2,3,4,5,6);

array.splice(0,0, 2)
result:2,1,2,3,4,5

3.var array = new Array(1,2,3,4,5,6);

array.splice(0,0,2,3,4)

2,3,4,1,2,3,4,5,6

1. Creation of array

var arr = new Array(); arr[0] = "aaa"; arr[1] = "bbb"; arr[2] = "ccc";

var a = [ 1,2,3,4,5];

var c = new Array("first", "second", "third");

Or array direct quantity:

var d = ["first", "second", "third"];

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 This method creates an array and specifies the length, but in fact the array is variable-length in all cases. That is to say, even if the length is specified to be 5, elements can still be stored outside the specified length. Note: At this time, the length will change accordingly. Change.

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

var a = new Array("first", "second", "third"); delete a[1]; document.write(a.length) //The displayed result is 3, indicating that the length of the array cannot be changed even if deleted

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. Array Interception and merging

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. Stringization of array elements

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：可以看作是join的特殊用法，不常用

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