If you’re working with arrays in JavaScript, you may encounter situations where your array contains undefined values. This can happen when you're processing data from various sources or working with incomplete datasets. One common problem developers face is summing the values of an array with undefined elements. JavaScript’s reduce() method is a versatile tool that can help you solve this problem efficiently. In this article, we will explore how to use the reduce() method to sum an array, even when it includes undefined values, and ensure that the final result is correct. What is the reduce() Method in JavaScript? The ... Read More

Let’s say, we have an array of arrays, each containing some numbers along with some undefined and null values. We are required to create a new array that contains the sum of each corresponding sub array elements as its element. And the values undefined and null should be computed as 0.Following is the sample array −const arr = [[    12, 56, undefined, 5 ], [    undefined, 87, 2, null ], [    3, 6, 32, 1 ], [    undefined, null ]];The full code for this problem will be −Exampleconst arr = [[    12, 56, undefined, 5 ... Read More

Let’s say, we have to write a function −replaceChar(str, arr, [char])Now, replace all characters of string str that are not present in array of strings arr with the optional argument char. If char is not provided, replace them with ‘*’.Let’s write the code for this function.The full code will be −Exampleconst arr = ['a', 'e', 'i', 'o', 'u']; const text = 'I looked for Mary and Samantha at the bus station.'; const replaceChar = (str, arr, char = '*') => {    const replacedString = str.split("").map(word => {       return arr.includes(word) ? word : char;    }).join("");   ... Read More

Let’s say, we have an array of objects that contains data about the humidity over the seven days of a week. The data, however, sits randomly in the array right now. We are supposed to sort the array of objects according to the days like data for Monday comes first, then Tuesday, Wednesday and lastly Sunday.Following is our array −const weather = [{    day: 'Wednesday',    humidity: 60 }, {    day: 'Saturday',    humidity: 50 }, {    day: 'Thursday',    humidity: 65 }, {    day: 'Monday',    humidity: 40 }, {    day: 'Sunday',    humidity: ... Read More

Let’s say, we are given an array of numbers that contains first n natural numbers, but one element appears twice in the array, so the total number of elements is n+1. Our job is to write a function that takes in the array and returns the number that appears twice in linear time.Method 1: Using Array.prototype.reduce()This is a bit trickier approach but the most compressed in terms of code written. First, let’s see the code for it −const arr = [1, 4, 8, 5, 6, 7, 9, 2, 3, 7]; const duplicate = a => a.reduce((acc, val, ind) => val+acc- ... Read More

We are required to write a function that takes in an array of numbers and returns the difference between its highest and lowest number.At first, create an array −const arr = [23, 54, 65, 76, 87, 87, 431, -6, 22, 4, -454];Now, find maximum and minimum values with Math.max() and Math.min() methods, respectively −const arrayDifference = (arr) => {    let min, max;    arr.forEach((num, index) => {       if(index === 0){          min = num;          max = num;       }else{          min = Math.min(num, min); ... Read More

Let’s say, we are required to write a function that takes in two arrays and returns a new array that contains values in alternating order from first and second array. Here, we will just loop over both the arrays simultaneously picking values from them one after the other and feed them into the new array.The full code for doing the same will be −Exampleconst arr1 = [34, 21, 2, 56, 17]; const arr2 = [12, 86, 1, 54, 28]; let run = 0, first = 0, second = 0; const newArr = []; while(run < arr1.length + arr2.length){    if(first ... Read More

Let’s say, we have an array of strings in which each value each element has a dash (-), left to which we have our key and right to which we have our value. Our job is to split these strings and form an object out of this array.Here is the sample array −const arr = ["name-Rakesh", "age-23", "city-New Delhi", "jobType-remote", "language-English"];So, let’s write the code, it will loop over the array splitting each string and feeding it into the new objectThe full code will be −Exampleconst arr = ["name-Rakesh", "age-23", "city-New Delhi", "jobType-remote", "language-English"]; const obj = {}; arr.forEach(string => ... Read More

We are required to write a function that takes in an array and returns a new array that have all duplicate values removed from it.The values that appeared more than once in the original array should not even appear for once in the new array.For example, if the input is −const arr = [23, 545, 43, 232, 32, 43, 23, 43];The output should be −const output = [545, 232, 32];Understanding the difference −Array.prototype.indexOf() → It returns the index of first occurrence of searched string if it exists, otherwise -1.Array.prototype.lastIndexOf() → It returns the index of last occurrence of searched string ... Read More

We are required to write a function that takes in a number between 1 and 26 (both inclusive) and returns the corresponding English alphabet for it. (capital case) If the number is out of this range return -1.For example −toAlpha(3) = C toAlpha(18) = RAnd so on.The ASCII CodesASCII codes are the standard numerical representation of all the characters and numbers present on our keyboard and many for.The capital English alphabets are also mapped in the ascii char codes, they start from 65 and goes all the way up to 90, with 65 being the value for ‘A’, 66 for ... Read More