Popular array handling methods (Array) in JavaScript (Part 3)

Hi guys, in part 1 and part 2 we learned about 15 methods of array.

In this article, I continue to introduce to you the methods that are quite important to the array that devjs often confuse when using the typical slice () with splice ().  Let’s get started

16. slice ()

slice() into Vietnamese is cut, sliced, sliced, bla bla, … and its function is also used to cut off some elements of the array.

slice() returns a shallow copy of a portion of the array as an array that receives index values from begin to end (excluding end).

• slice() NOT change the original array
• slice() returns a new array after cutting

With positive index

With negative index

Pretty twisted brain with this yin and yang

Syntax

17. splice ()

splice() used to change elements of an array by deleting an existing element or adding a new element

• splice() YES changes the original array
• splice() returns the array containing the deleted elements

This is a rather confusing row when it can both add an element, just delete the element and change it directly on the original array, so if you do not control the arguments passed, it will be opened immediately. See the following example

Delete the element with the start argument

Delete element with additional deleteCount argument (deleteCount: specifies the number of elements to be deleted)

Add the element with the 3rd argument

Add more items

It is not difficult, right, focus is absorbed, sometimes the deadline is about to forget slightly

Syntax

18. Array.from ()

Array.from() used to create a new array of words

• object is like array (object has length and elements are indexed)
• iterable objects (objects can get its elements, like Map and Set )

Array.from() returns a new array

Syntax

19. Array.isArray ()

Array.isArray() used to check if the input value is an Array type Array

• Array.isArray() returns Boolean type: true if array and false if not array

Syntax

summary

Grab the skirt, we have the following summary

Method	Function	Return value	Change the original array
concat ()	Concatenate 2 or more arrays	New array after joining	Is not
filter ()	Filter out the elements that satisfy the condition	New arrays after filtering	Is not
find()	Filter out the first element that satisfies the condition	The value FIRST found / undefined	Is not
forEach ()	Browse through each element of the array	undefined	–
includes ()	Checks whether the element exists in the array	true / false	Is not
indexOf ()	Finds the position of an element in an array	Index FIRST found / -1	Is not
join()	Create a new string	New string / That element / ""	Is not
map()	Create a new array by changing the original array	New arrays after transformation	Is not
pop()	Remove the last element from the array	The element has been removed / undefined	Have
shift ()	Remove the first element from the array	The element has been removed / undefined	Have
push()	Add 1 or more elements to the end of the array	NEW LEVELS of array	Have
unshift ()	Add 1 or more elements to the beginning of the array	NEW LEVELS of array	Have
reduce ()	Execute the function on each element to get a value	Value after abridged	Is not
reverse ()	Reverse the array	Array after reversing	Have
some()	Check that at least 1 element satisfies the condition	true / false	Is not
sort()	Arrange the elements in the array	Arrays after being sorted	Have
slice ()	Cut off some elements of the array	New arrays after cutting	Is not
splice ()	Add / remove elements in the array	The array contains the deleted elements	Have
Array.from ()	Create a new array	New array	–
Array.isArray ()	Check if the input value is an array	true / false	–

Conclude

Ok it seems enough, there are some other methods but I find it used so it should not list, if you want to be able to find documents online. Hopefully after reading this series you can master the array, a row will be used a lot with devjs.

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See you in the following posts!