Write a function that converts a number to a string with commas separating thousands in JavaScript.
Write a function that removes the first occurrence of a specified element from an array in JavaScript.
Write a function that returns the last n elements of an array in JavaScript.
Write a function that generates a random alphanumeric string of a specified length in JavaScript.
Write a function that returns the sum of all numbers in an array in JavaScript.
Write a function that sorts an array of objects by a specified property in JavaScript.
Write a function that returns the longest word in a string in JavaScript.
Write a function that converts a string to title case (i.e., capitalizes the first letter of each word) in JavaScript.
Write a function that returns the number of occurrences of a specified element in an array in JavaScript.
Write a function that checks whether a given string is a palindrome (i.e., reads the same forwards and backwards) in JavaScript.
Write a function that finds the first non-repeating character in a string in JavaScript.
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Write a function that converts a number to a string with commas separating thousands in JavaScript.
function addCommas(num) {
return num.toString().replace(/\B(?=(\d{3})+(?!\d))/g, “,”);
}
Explanation: The function first converts the input number to a string using the toString() method. Then, it uses a regular expression (/\B(?=(\d{3})+(?!\d))/g) to match any digits that are not preceded by the beginning of a number (\B) and are followed by groups of three digits ((\d{3})+) that are not followed by more digits ((?!\d)). The replace() method then replaces each match with a comma.
Write a function that removes the first occurrence of a specified element from an array in JavaScript.
function removeElement(arr, element) {
const index = arr.indexOf(element);
if (index > -1) arr.splice(index, 1);
return arr;
}
Explanation: The function uses the indexOf() method to find the index of the first occurrence of the specified element in the input array. If it exists (i.e., its index is greater than -1), the splice() method is used to remove it from the array.
Write a function that returns the last n elements of an array in JavaScript.
function lastNElements(arr, n) {
return arr.slice(-n);
}
Explanation: The function uses the slice() method with a negative index to return the last n elements of the input array.
Write a function that generates a random alphanumeric string of a specified length in JavaScript.
function generateRandomString(length) {
const chars = “abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789”;
let result = “”;
for (let i = 0; i < length; i++) {
result += chars.charAt(Math.floor(Math.random() * chars.length));
}
return result;
}
Explanation: The function generates a random alphanumeric string of the specified length by first creating a string of all possible characters
Write a function that returns the sum of all numbers in an array in JavaScript.
function sumArray(arr) {
return arr.reduce((total, num) => total + num, 0);
}
Explanation: The function uses the reduce() method to add up all the numbers in the input array, starting with an initial value of 0.
Write a function that sorts an array of objects by a specified property in JavaScript.
function sortByProperty(arr, property) {
return arr.sort((a, b) => a[property] – b[property]);
}
Explanation: The function sorts an array of objects by a specified property using the sort() method with a custom comparison function that subtracts the property value of the second object from that of the first object.
Write a function that returns the longest word in a string in JavaScript.
function longestWord(str) {
const words = str.split(” “);
return words.reduce((longest, word) => (word.length > longest.length ? word : longest), “”);
}
Explanation: The function first splits the input string into an array of words using the split() method. It then uses the reduce() method to compare the length of each word to the current longest word and return the longest one.
Write a function that converts a string to title case (i.e., capitalizes the first letter of each word) in JavaScript.
function toTitleCase(str) {
return str.replace(/\b\w/g, match => match.toUpperCase());
}
Explanation: The function uses a regular expression (/\b\w/g) to match the first letter of each word in the input string (\b matches a word boundary and \w matches a word character). The replace() method then replaces each match with its uppercase equivalent using a callback function.
Write a function that returns the number of occurrences of a specified element in an array in JavaScript.
function countOccurrences(arr, element) {
return arr.filter(item => item === element).length;
}
Explanation: The function uses the filter() method to create a new array containing only the occurrences of the specified element and then returns its length.
Write a function that checks whether a given string is a palindrome (i.e., reads the same forwards and backwards) in JavaScript.
function isPalindrome(str) {
const reversed = str.split(“”).reverse().join(“”);
return str === reversed;
}
Explanation: The function first reverses the input string by splitting it into an array of characters, reversing the array, and joining it back into a string. It then compares the original string to the reversed string and returns true if they are the same.
Write a function that finds the first non-repeating character in a string in JavaScript.
function firstNonRepeatingChar(str) {
const counts = {};
for (const char of str) {
counts[char] = counts[char] ? counts[char] + 1 : 1;
}
for (const char of str) {
if (counts[char] === 1) {
return char;
}
}
return null;
}
Explanation: The function first creates an object to store the number of occurrences of each character in the input string. It then iterates through the string twice: once to count the occurrences of each character and once to find the first character with a count of 1.