# ◉ sum of no.s using Recursion

`var array_sum = function(arr) {  if (arr.length === 1) {    return arr;  }  return arr.pop() + array_sum(arr);  };console.log(array_sum([1,2,3,4,5,6]));# 21`
`// functional approachconst log = message => console.log(message);`
`const increaseByOne = num => num + 1;const num = 1const newNum = increaseByOne(num) // => 2console.log(num) // => 1`
`const sum = (a,b) => a + bconst average = (fn, ...nums) => nums.reduce(fn) / nums.length;const numsAvg = average(sum, 1, 2, 3) // => 2`

## ◉ sum of (numbers) when you don’t know how many numbers are there in advance…rest operator.

`const sum = (...args)=>{ return args.reduce((a, b) => a+b);  // args.length will return '4' here; }console.log(sum(2,3,4,6));# 15`

# (…) Rest parameter syntax

`function numbers(x,y, ...z){    console.log(x,y,z);}numbers(1,2,3,4,5,6);# Output: 12[3,4,5,6]`

`function getSum(x, y, z){   console.log(x+y+z);}let arr = [10,20,30];getSum(...arr);`

# ◉ Getting key with the highest value from object

`var obj = {a: 1, b: 2, undefined: 1};Object.keys(obj).reduce(function(a, b){ return obj[a] > obj[b] ? a : b });`

# ◉ find the most frequent item in an array

`Write a JavaScript program to find the most frequent item of an array. Search should be case insensitive.input: [1, 'T', 'a', 'T', 2, 3, 'T', 3, 't', 2, 't', 9, 3];output: t = 5`

## ◉ Count the occurrence of each character in a string

`var str = "count number of each char in this string";var obj = {};// Misc varsvar ch, index, len, count;for (index = 0, len = str.length; index < len; ++index) {    ch = str.charAt(index);     count = obj[ch];    console.log("count =>"+ count); // "count =>undefined"    obj[ch] = count ? count + 1 : 1;}for (ch in obj) {    console.log(ch + " ==>: " + obj[ch]);}`

## ◉ reverse a “string” using inbuilt methods

`function reverseString(str) {    return str.split("").reverse().join("");}reverseString("hello");`

## ◉ reverse an INTEGER using inbuilt methods

`let myNumber = 23;let myChar = myNumber.toString().split('').reverse().join('');console.log(myChar)   // returns 32;console.log(typeof(myChar)) // returns string`
`const myNewNumber = parseInt(myChar);console.log(myNewNumber); // returns 32console.log(typeof(myNewNumber)) // returns number`

# ◉ Don’t Use If-Else and Switch in JavaScript, Use Object Literals

`var arr = [2,3,4,5];arr.getSum = function() {    var sum= 0;   for(var i=0; i< arr.length; i++){      sum = sum + arr[i];   };   console.log(sum);}arr.getSum();Attach a function to array in js?let tempArray = [6, 2, 3, 4, 5];let averageValues = tempArray.average();console.log(averageValues); // should return average of tempArray`

Experience with Front-end Technologies and MERN / MEAN Stack. Working on all Major UI Frameworks like React, Angular.

## More from Anil Kumar

Experience with Front-end Technologies and MERN / MEAN Stack. Working on all Major UI Frameworks like React, Angular.