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This article mainly explains "what is the use of JS array". Interested friends may wish to have a look at it. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn how to use JS array.

First, the original array 1.push () is modified:

(at the end of the array) add a new element to the array

The push () method returns the length of the new array

Var fruits = ["Banana", "Orange", "Apple", "Mango"]; fruits.push ("Kiwi"); 2.pop ():

Method to remove the last element from the array

You can receive the return value of pop (), which is the pop-up value "Mango"

Var fruits = ["Banana", "Orange", "Apple", "Mango"]; fruits.push ("Kiwi"); 3.shift ():

Delete the first array element

You can receive deleted values

Var fruits = ["Banana", "Orange", "Apple", "Mango"]; fruits.shift (); 4.unshift ():

(at the beginning) add a new element to the array

Returns the length of the new array.

Var fruits = ["Banana", "Orange", "Apple", "Mango"]; fruits.unshift ("Lemon"); 5.splice ():

Used to add new items to the array

The first parameter (2) defines where the new element should be added (splicing).

The second parameter (0) defines how many elements should be deleted.

The remaining parameters ("Lemon", "Kiwi") define the new elements to be added.

The splice () method returns an array of deleted items

You can also delete elements in the array by setting parameters

Var fruits = ["Banana", "Orange", "Apple", "Mango"]; fruits.splice (2,0, "Lemon", "Kiwi"); / / ["Banana", "Orange", "Lemon", "Kiwi", "Apple", "Mango"] var fruits = ["Banana", "Orange", "Apple", "Mango"]; fruits.splice (0,1); / / [Orange "," Apple "," Mango "] 6.sort ():

Sort the array alphabetically

If you are sorting numbers, you need to be careful. "25" is greater than "100" because "2" is greater than "1". We use a ratio function to correct this problem.

Sort () can also sort the array of objects by modifying the comparison function.

Var fruits = ["Banana", "Orange", "Apple", "Mango"]; fruits.sort (); var points = [40,100,1,5,25,10]; points.sort (function (a, b) {return a-b}); / / ascending points.sort (function (a, b) {return b-a}); / / descending points.sort ((a, b) = > {return b-a}) / Arrow function var cars = [{type: "Volvo", year:2016}, {type: "Saab", year:2001}, {type: "BMW", year:2010}] cars.sort (function (a, b) {return a.year-b.year}); / / comparison year (number) cars.sort (function (a, b) {/ / comparison type (string) var x = a.type.toLowerCase () Var y = b.type.toLowerCase (); if (x

< y) {return -1;} if (x >

Y) {return 1;} return 0;}); 7.reverse ():

Invert elements in an array

Var fruits = ["Banana", "Orange", "Apple", "Mango"]; fruits.reverse (); second, do not modify the original array 1.toString ():

Converts an array to a comma-separated string of array values.

Var fruits = ["Banana", "Orange", "Apple", "Mango"] console.log (fruits.toString ()) / / Banana,Orange,Apple,Mango2.join ():

All array elements can be combined into a single string.

It behaves like toString (), but it can also specify a delimiter

Var fruits = ["Banana", "Orange", "Apple", "Mango"] console.log (fruits.join ("*")) / / Banana * Orange * Apple * Mango3.concat ():

Create a new array by merging (joining) existing arrays. You can connect multiple

Var myGirls = ["Cecilie", "Lone"]; var myBoys = ["Emil", "Tobias", "Linus"]; var myChildren = myGirls.concat (myBoys); / / Connect myGirls and myBoys var arr1 = ["Cecilie", "Lone"]; var arr2 = ["Emil", "Tobias", "Linus"]; var arr3 = ["Robin", "Morgan"]; var myChildren = arr1.concat (arr2, arr3) / / connect arr1, arr2 and arr3 together 4.slice ():

Method to cut out a new array with a fragment of the array.

Var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"]; var citrus = fruits.slice (1); / / from the first to the last / ["Orange", "Lemon", "Apple", "Mango"] var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"]; var citrus = fruits.slice (1) / / from the first to the third (excluding 3) / / ["Orange", "Lemon"] 5.map ():

Call a supplied function for each element in the array, and the result is returned as a new array without changing the original array.

Let arr= [1,2,3,4,5] let newArr = arr.map (x = > xan2) / / the abbreviated arrow function / / arr= [1,2,3,4,5] the original array remains unchanged / / newArr = [2,4,6,8,10] returns the new array 6.forEach ():

Execute the provided function for each element in the array with no return value, which should be distinguished from the map method

Let arr = [1, 2, 3, 4, 5] arr.forEach (x = > {console.log (2x2) / / return xchang2 return value is useless, this function does not return value}) 7.filter ():

This method judges all the elements and returns the elements that meet the criteria as a new array. The condition is written in the function!

Let arr = [1, 2, 3 return value 4 newArr 5] let newArr = arr.filter (value = > value > = 3) / / or let newArr = arr.filter (function (value) {return value > = 3}) console.log (newArr) / / [3meme 4 Magi 5] 8.every ():

This method returns a Boolean value after judging all elements, and returns true if all elements meet the judgment condition, otherwise it is false

Let arr = [1,2,3,4,5] const isLessThan4 = value = > value

< 4const isLessThan6 =>

Value = > value

< 6arr.every(isLessThan4 ) //falsearr.every(isLessThan6 ) //true9.some(): 此方法是将所有元素进行判断返回一个布尔值，如果存在元素满足判断条件，则返回true，若所有元素都不满足判断条件，则返回false let arr= [1, 2, 3, 4, 5]const isLessThan4 = value =>

Value

< 4const isLessThan6 = value =>

Value > 6arr.some (isLessThan4) / / truearr.some (isLessThan6) / / false10.reduce ():

This method is that all elements call the return function, the return value is the final result, and the value passed in must be a function type.

Let arr = [1, 2, 3, 4, 5] const add = (a, b) = > a + blet sum = arr.reduce (add) console.log (sum) / / sum = 15 is equivalent to the cumulative effect / / corresponding to an Array.reduceRight () method, the difference is that this is operated from right to left so far, I believe you have a deeper understanding of the "what use of the JS array", you might as well come to the actual operation! Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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