What are the array operations in js? Summary of methods for operating arrays in js

This article brings you what are the array operations in js? A summary of the methods of operating arrays in js has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Preface

We often need to perform various operations on arrays, such as inserting an item at the front of the array, inserting an item at the end, inserting an item in the middle, etc. Then do these operations at once!

First item related operations

First item insertion: unshift

let myArray = [1, 2, 3]
myArray.unshift(0) //插入项的值为0
myArray

##First item Item deletion:

shift

let myArray = [1, 2, 3]
myArray.shift()
myArray

Last item related operations

Last item insertion:

push

let myArray = [1, 2, 3]
myArray.push(4) // 插入项的值为4
myArray

##Delete the last item:

pop

<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">let myArray = [1, 2, 3] myArray.pop() // 弹出最后一项 myArray</pre><div class="contentsignin">Copy after login</div></div>

Intermediate item related operations

Insert one or more items at the i-th position:

splice

<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">let myArray = ['a', 'b', 'c'] myArray.splice(1, 0, '哈哈哈', '嚯嚯嚯', '嘻嘻嘻') myArray</pre><div class="contentsignin">Copy after login</div></div>

Explain the

splice

method to understand it. splice can be used to delete an array or add elements, and receives more than two parameters: Position , How many items to delete, Items to insert. Therefore, myArray.splice(1, 0, 'Hahaha', '嚯嚯嚯', 'heeheehee') is translated as: At the position with the subscript 1, delete the 0 item and replace it with Hahaha, 嚯嚯嚯, heeheeheeInsert. In this way, you can only add and not delete.

Delete items i to j:

---

splice

<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">let myArray = ['a', 'b', 'c', 'd', 'e'] myArray.splice(1, 3) // 删除b, c, d myArray</pre><div class="contentsignin">Copy after login</div></div>

Face splice according to the above For explanation, you can know that

myArray.splice(1, 3)

means starting from the array subscript 1, deleting 3 elements (without doing any insertion)

Only keep items i to j:

---

slice

<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">let myArray = ['a', 'b', 'c', 'd', 'e'] myArray = myArray.slice(2, 4) myArray</pre><div class="contentsignin">Copy after login</div></div>

##Explanation of slice

: replace slice It is understood as sliding selection and receives two parameters,

start position and end position, that is, slide out the elements from the start position to the end position in the array (excluding the end position) Element) , returned as the return value. Therefore myArray = myArray.slice(2, 4)The translation is from the element with subscript 2 to subscript 3 (note that the subscript here is 3 instead of 4)## The element of # slides out and is returned as the return value and reassigned to myArray. The comparison between slice and split will be discussed in detail later. Summary: Mainly talk about the difference between splice and slice. I won’t talk about the functional difference. I will just talk about a few points to pay attention to:

splice will change the original Arrays, but slice does not, so you need to reassign the value after completing the operation with slice.

• The two parameters received by slice are

  2
and # When ##4
• , the final result is the element

  with subscript 2 to subscript 3 (excluding 4) understand slice For sliding, it will not be recorded.

• Related recommendations:

Summary of js array operation methods (must read)

js Common methods for array operations

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