In JavaScript, array is a special type of variable that
allows you to store multiple values in a single variable.
Here are 10 javascript array methods you should at least
know
#splice()
Adds/Removes elements from particular location of an array.
let arr = ["I", "love", "JS"];
arr.splice(1, 1); // from index 1 remove 1 element
alert( arr ); // ["I", "JS"]
The splice method is also able to insert the elements
without any removals. For that we need to set deleteCount to
0:
let arr = ["I", "study", "JS"];
// from index 2
// delete 0
// then insert "complex" and "language"
arr.splice(2, 0, "complex", "language");
alert( arr ); // "I", "study", "complex", "language", "JS"
#forEach()
This method can help you to loop over array's items.
const num = [1, 2, 3, 4, 5, 6];
num.forEach(item => {
console.log(item); // output: 1 2 3 4 5 6
});
#filter()
This method create new array with only elements passed
condition inside the provided function.
const num = [1, 2, 3, 4, 5, 6];
// item(s) greater than 3
const filtered = num.filter(num => num > 3);
console.log(filtered); // output: [4, 5, 6]
console.log(num); // output: [1, 2, 3, 4, 5, 6]
#map()
This method create new array by calling the provided
function in every element.
const num = [1, 2, 3, 4, 5, 6];
// add one to every element
const oneAdded = num.map(num => num + 1);
console.log(oneAdded); // output [2, 3, 4, 5, 6, 7]
console.log(num); // output: [1, 2, 3, 4, 5, 6]
#push()
Adding Element at the end of an Array. As array in
JavaScript are mutable object, we can easily add or remove
elements from the Array. And it dynamically changes as we
modify the elements from the array.
// Adding elements at the end of an array
// Declaring and initializing arrays
var number_arr = [ 10, 20, 30, 40, 50 ];
var string_arr = [ "a", "b", "c", "d" ];
// push()
// number_arr contains [10, 20, 30, 40, 50, 60]
number_arr.push(60);
// We can pass multiple parameters to the push()
// number_arr contains
// [10, 20, 30, 40, 50, 60, 70, 80, 90]
number_arr.push(70, 80, 90);
// string_arr contains
// ["a", "b", "c", "d", "y", "x"];
string_arr.push("y", "x");
// Printing both the array after performing push operation
console.log("After push op " + number_arr);
console.log("After push op " + string_arr);
#pop()
Removing elements from the end of an array.
// Removing elements from the end of an array
// Declaring and initializing arrays
var number_arr = [ 20, 30, 40, 50 ];
var string_arr = [ "x", "y", "z" ];
// pop()
// number_arr contains
// [ 20, 30, 40 ]
number_arr.pop();
// string_arr contains
// ["x", "y"]
string_arr.pop();
// Printing both the array after performing pop operation
console.log("After pop op " + number_arr);
console.log("After popo op " + string_arr);
#reduce()
The reduce() method applies a function against an
accumulator and each element in the array (from left to
right) to reduce it to a single value - MDN
const arr = [1, 2, 3, 4, 5, 6];
const sum = arr.reduce((total, value) => total + value, 0);
console.log(sum); // 21
#shift()
Removing elements at the beginning of an array
// Removing element from the beginning of an array
// Declaring and initializing arrays
var number_arr = [ 20, 30, 40, 50, 60 ];
var string_arr = [ "x", "y", "z", "a" ];
// shift()
// number_arr contains
// [30, 40, 50, 60];
number_arr.shift();
// string_arr contains
// ["y", "z", "a"]
string_arr.shift();
// Printing both the array after performing shifts operation
console.log("After shift op " + number_arr);
console.log("After shift op " + string_arr);
