Array's Methods Part 2.

As we talked about unshift, shift, push, pull and splice in the previous article, now we're going to talk about some other methods in points:

• Array has Some methods that we use to sort it:-

1. sort():sorts the array's eles alphabetically or increasingly :
2. reverse():reascend the array in reverse:

let arrTest = [5, 4, 3, 7, 1]
console.log(arrTest.sort()) // [1,3,4,5,7]
let arrTest = [5, 4, 3, 7, 1]
console.log(arrTest.reverse()) // [1,7,3,4,5]
let arrTest = [5, 4, -1, 3, 7, -2, 1]
console.log(arrTest.sort())
console.log(arrTest.sort((a,b) => a - b)) // [1,3,4,5,7]
console.log(arrTest.sort((a,b) => b - a)) // [7,5,4,3,1] => sort().reverse()
arrTest = ['d', 'a', 'c']
console.log(arrTest.sort()) // ['a', 'c', 'd']
console.log(arrTest.reverse()) // ['d', 'c', 'a'        

• Some methods that make it more Easy to deal with them by indexes or values:

1. indexof():returns the first Value's index it meets, it takes 2 args (the value we are searching for, the starting idx(opt.)), so if we have an array with duplicate values it returns the first one's idx.
2. lastIndexOf():this works better with arrays that have duplicate values, it's same as indexOf() but returns the last idx of the value

PS: if we entered a value that's not in the array, they'll return -1

let arrTest = [5, 4, 3, 7, 3, 1, 3, 8]
console.log(arrTest.indexOf(3)) // 2
console.log(arrTest.lastIndexOf(3)) // 6
console.log(arrTest.indexOf(55)) // -1        

• includes():this method assure if a the array contains a certain value or not. takes 2 args too (value, start idx) , returns true if exists, false otherwise.

search for find() and filter() methods too .

console.log(arrTest.includes(4)) // true

console.log(arrTest.filter((element) => element > 4)) // any element that elligeble for the condition 
// if the element doesn't exist it returns empty array []
console.log(arrTest.find((element) => element > 5)) // the first element that's elligible for the cond
// if the element doesn't exist it returns undefined
        

• concat():merges arrays in one array.

arr1 = [1,2,3]
arr2 = [4,2,5]
arr3 =['a', 'b', 'c']
console.log(arr1.concat(arr2, arr3)) // [ 1, 2, 3, 4, 2, 5 ]        

• slice():returns a portion of the array, takes two args (startIdx, endIdx'not included') which means it slices till it gets to the idx before the endidx:

arr = [1,2,3,4,5,6,7,8]
console.log(arr.slice(0,3)) // [1,2,3] => endidx is n't includded

arrCopy = arr.slice(0, -1) 
console.log(arrCopy) [1,2,3,4,5,6,7,8]        

• join():this methods returns a string representation for the array's values. it works the opposite of Array.from() we talked about in creating arrays , takes one arg as the separator, its default separator is comma.

arrTest = ['k','h','o','l','o','u','d']
console.log(arrTest.join('-')) // k-h-o-l-o-u-d
console.log(arrTest.join('')) // kholoud

let n = arrTest.join('')

console.log(Array.from('mohamed')) // ['m', 'o', 'h', 'a', 'm', 'e', 'd']

console.log('mohamed'.split('')) // =>strtok() // ['m', 'o', 'h', 'a', 'm', 'e', 'd']
        

• every():this method iterates over every ele in the array and test if the condition of the function passed all of it or not, if yes returns true, otherwise returns false. [kind if checking if ele1 true && ele2 true && ...etc]
• some():some() method works same as every() method but it returns true if some of its eles passed the condition and false if NONE of them passed it [kind if checking if ele1 true || ele2 true || ...etc]

arrTest = [2,4,6,7]
console.log(arrTest.every((number) => number % 2 === 0)) // false
console.log(arrTest.some((number) => number % 2 === 0)) // true        

• map():this method is one of the commonly used method in arrays, it returns a new array with the result of calling a function on every element in the array, which means it just pushes the result of passing a condition to a new array.

arrTest = [1,2,3,4]
mapRes = arrTest.map((el) => el * 2)
console.log(mapRes) // [2, 4, 6, 8]

arrTest = [10,21,30,60]

console.log(arrTest.map((number) => number > 50 ? number * 2 : number % 2 ===0? number / 2 : number)) //?[5, 21, 15, 120]        

• forEach():this method is like your arm in coding in js using arrays :D, it iterates over every eles of the array and executes the function passed into it.

arr = ['a', 'b', 'c'];

arr.forEach((element) => console.log(element)); // a
                                                // b
                                                // c        

PS: those methods and most of the Array's methods are called 'Iterative methods' which means they take a callback function(mostly the arrow function) as argument and mostly this function is called for every element in the array, it determines the return value of the entire method.

Now i think i mentioned the widely most used array's methods, and you can check the various methods array has through this great site, it was a great resource for me to get deep understanding of array's methods. : Array - JavaScript | MDN (mozilla.org)

Thank You For Your Time!.