JS Array.slice implementation method of intercepting array

JS Array.slice implementation method of intercepting array_javascript skills

WBOY

Release： 2016-05-16 15:22:23

Original

1648 people have browsed it

slice definition and usage

The slice() method returns selected elements from an existing array.

Grammar
arrayObject.slice(start,end)

参数	描述
start	必需。规定从何处开始选取。如果是负数，那么它规定从数组尾部开始算起的位置。也就是说，-1 指最后一个元素，-2 指倒数第二个元素，以此类推。
end	可选。规定从何处结束选取。该参数是数组片断结束处的数组下标。如果没有指定该参数，那么切分的数组包含从 start 到数组结束的所有元素。如果这个参数是负数，那么它规定的是从数组尾部开始算起的元素。

Return value

Returns a new array containing the elements in arrayObject from start to end (exclusive).

Description

Please note that this method does not modify the array, but returns a subarray. If you want to delete a segment of elements from an array, you should use the method Array.splice().

Tips and Notes

Note: You can use negative values to select elements from the tail of an array.
Note: If end is not specified, the slice() method selects all elements from start to the end of the array.

Example

Example 1

In this example we will create a new array and then display the elements selected from it:

<script type="text/javascript">

var arr = new Array(3)
arr[0] = "George"
arr[1] = "John"
arr[2] = "Thomas"

document.write(arr + "<br />")
document.write(arr.slice(1) + "<br />")
document.write(arr)

</script>

Copy after login

Output:
George,John,Thomas
John,Thomas
George,John,Thomas

Example 2

In this example we will create a new array and then display the elements selected from it:

<script type="text/javascript">

var arr = new Array(6)
arr[0] = "George"
arr[1] = "John"
arr[2] = "Thomas"
arr[3] = "James"
arr[4] = "Adrew"
arr[5] = "Martin"

document.write(arr + "<br />")
document.write(arr.slice(2,4) + "<br />")
document.write(arr)

</script>

Copy after login

Output:
George,John,Thomas,James,Adrew,Martin
Thomas,James
George,John,Thomas,James,Adrew,Martin

Core code:

<script type="text/javascript">
//JS Array.slice 截取数组
//在JavaScript中，Array对象的slice(start[,end])方法返回数组从下标[start,end)的部分（不包含下标为end的元素）如果没有指定end参数，则从start开始到数组结尾的部分，slice()方法不改变原数组，如果要删除数组的一部分，可以使用splice()方法。
//参数：
//（1）start:开始截取的数组下标，如果start是负数，表明从数组尾部开始计算。
//（2）end:结束截取的数组下标，如果end是负数，表明从数组尾部开始计算。
//例1：

var arr = [1,2,3,4,5,6,7,8,9];
    // [0,1,2,3,4,5,6,7,8]
  // [-10,-9,-8,-7,-6,-5,-4,-3,-2,-1]
  
document.writeln(arr.slice(5)); // 输出：6,7,8,9
document.writeln(arr.slice(-5)); // 输出：5,6,7,8,9
document.writeln(arr.slice(0,3)); // 输出：1,2,3
document.writeln(arr.slice(1,2)); // 输出：2
document.writeln(arr.slice(3,-2)); // 输出：4,5,6,7
document.writeln(arr.slice(1,9999)); // 输出：2,3,4,5,6,7,8,9
//==================================================================================================
//JS Array.splice(start,delete_count,value,...) 插入、删除、替换数组
//参数：
//（1）start:开始插入和（或）删除的数组元素的下标。
//（2）delete_count:结束截取的数组下标，如果end是负数，表明从数组尾部开始计算。
//（3）value,...：要插入数组的元素。
//返回：如果从数组中删除了元素，则返回的是被删除的元素的数组
//
//例1：
document.write("<hr>");
//
var arr = [1,2,3,4,5,6,7,8,9];
document.writeln("arr=" + arr); // 输出：arr=1,2,3,4,5,6,7,8,9
document.writeln("arr.splice(5)=" + arr.splice(5)); // 输出：arr.splice(5)=6,7,8,9
document.writeln("arr=" + arr); // 输出：arr=1,2,3,4,5
document.write("<br>");
//
var arr = [1,2,3,4,5,6,7,8,9];
document.writeln("arr=" + arr); // 输出：arr=1,2,3,4,5,6,7,8,9
document.writeln("arr.splice(5,1,99,100)=" + arr.splice(5,1,99,100)); // 输出：arr.splice(5,1,99,100)=6
document.writeln("arr=" + arr); // 输出：arr=1,2,3,4,5,99,100,7,8,9
document.write("<br>");
</script>

Copy after login

Okay, actually use array.alice(0,20); to intercept the first 20.