Array object

1. Method of not changing the original array

concat()

The concat() method is used to join two or more arrays.

Parameter: required. This parameter can be a concrete value or an array object. It can be any number.

Return value: returns the connected new array

var hege = ["Cecilie", "Lone"];
var stale = ["Emil", "Tobias", "Linus"];
var kai = ["Robin"];
var children = hege.concat(stale,kai);

result: Cecilie,Lone,Emil,Tobias,Linus,Robin

join()

The join() method is used to convert all elements in the array into a string.

Parameter: optional. Specifies the delimiter to use. If this parameter is omitted, a comma is used as the separator.

Return value: returns the connected string

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var energy = fruits.join();

result: Banana,Orange,Apple,Mango

slice()

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

The slice() method extracts a part of a string and returns the extracted part with a new string.

Parameter: optional. array.slice(start, end) . If this parameter is omitted, all are intercepted.
Is a positive number: starting subscript (0) - > ending subscript (excluding)
Negative number: start (1) - > end (excluding)

Return value: returns the intercepted new array

var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
var citrus = fruits.slice(1,3);

result: Orange,Lemon

var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
var myBest = fruits.slice(-3,-1); // Intercept the two elements from the penultimate (inclusive) to the penultimate (exclusive)
var myBest = fruits.slice(-3);  // Intercept the last three elements

result: Lemon,Apple

2. Method of changing the original array

unshift()

The unshift() method adds one or more elements to the beginning of the array and returns a new length.

Parameter: required. Adds one or more elements to the start of the array.

Return value: returns the length of the new array

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Lemon","Pineapple");

result: Lemon,Pineapple,Banana,Orange,Apple,Mango

push()

The push() method adds one or more elements to the end of the array and returns a new length.

Parameter: required. The element to add to the array.

Return value: returns the length of the new array

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Kiwi")

result: Banana,Orange,Apple,Mango,Kiwi

shift()

The shift() method removes the first element of the array from it and returns the value of the first element.

Return value: returns the deleted element

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.shift()

result: Orange,Apple,Mango

pop()

The pop() method deletes the last element of the array and returns the deleted element.

Return value: returns the deleted element

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.pop();

result: Banana,Orange,Apple

splice()

The splice() method is used to add or remove elements from the array.

Parameter: required, optional, optional. array.splice(index,howmany,item1,.....,itemX) .
index: where to add / remove elements. Starting subscript
howmany: specifies how many elements should be deleted, which can be "0"
Item1,..., itemx: the new element to be added to the array

Return value: if the element is deleted, the deleted element is returned

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.splice(2,0,"Lemon","Kiwi");

result: Banana,Orange,Lemon,Kiwi,Apple,Mango

reverse()

The reverse() method is used to reverse the order of the elements in the array.

Return value: array after reverse order

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.reverse();

result: Mango,Apple,Orange,Banana

sort()

The sort() method is used to sort the elements of the array.

Parameter: optional. Specify the sort order. Must be a function.

Return value: changed array

// Alphabetic ascending order
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.sort();

result: Apple,Banana,Mango,Orange

// Numeric ascending order
var points = [40,100,1,5,25,10];
points.sort(function(a,b){return a-b});

Result: 100,40,25,10,5,1

// Number descending order
var points = [40,100,1,5,25,10];
points.sort(function(a,b){return b-a});

Results: 1,5,10,25,40,100