Array is zero-indexed, used for storing a collection of different data types under a single variable name.
let arr = [10,15,20,25];
let arr1 = new Array(1,2,3,4,5);
let arr2 = new Array(5).fill(10);
console.log(arr[2]); // returns 3rd element - 20
length - returns array length push - adds element to end arr.push(30); // [ 10, 15, 20, 25, 30 ]
shift - removes first element arr.shift(); // [ 15, 20, 25, 30 ]
unshift - add new element as first element arr.unshift(5); // [ 5, 15, 20, 25, 30 ]
pop - removes last element arr.pop(); // [ 5, 15, 20, 25 ]
lastIndexOf - returns index from end let arr5 = [40, 60, 50, 40, 30, 40]
let lastIndex = arr5.lastIndexOf(40); // 5
find - returns first element which matches condition arr.find((ele) => ele > 15 ) // 20
findIndex - returns first index matches condition arr.findIndex((ele) => ele > 15 ) // 2
includes - if array has that value returns true else false. arr.includes(20); // true
filter - returns array of elements matching condition arr.filter((ele) => ele < 30 ) // [ 5, 15, 20, 25 ]
some - validates atleast one element matches condition arr.some((ele) => ele % 10 === 0); // true
every - validates all elements match the condition arr.every((ele) => ele % 10 === 0); // false
map - creates a new array with resultant elements from function. arr.map((x) => x *5); // [ 50, 75, 100, 125 ]
reduce - runs a "reducer" callback function over all elements, in ascending-index order, and accumulates them into a single value. arr.reduce(((accu,curVal) => accu + curVal), 0); // 70
reverse - reverses an array in place and returns the reference to the same array. arr.reverse(); // [ 25, 20, 15, 10 ]
sort - sorts stringified elements of an array in place and returns the reference to the same array arr.sort(); // [ 10, 15, 20, 25 ]