🔧 JavaScript interview questions & answers with code
Nachrichtenbereich: 🔧 Programmierung
🔗 Quelle: dev.to
Top JavaScript Interview Questions and Expert Answers with Code Examples
Flatten a Nested Object
Question : Write a function to flatten a nested JavaScript object.
Code :
function flattenObject(obj, prefix = '', res = {}) {
** for (let key in obj) {**
** const newKey = prefix ? ${prefix}.${key} : key;**
** if (typeof obj[key] === 'object' && obj[key] !== null) {**
** flattenObject(obj[key], newKey, res);**
** } else {**
** res[newKey] = obj[key];**
** }**
** }**
** return res;**
}
console.log(flattenObject({ a: { b: { c: 1 } }, d: 2 }));
// Output: { 'a.b.c': 1, d: 2 }
2. Find Duplicates in an Array
Question : Write a function to find duplicate values in an array.
Code :
function findDuplicates(arr) {
** const counts = {};**
** return arr.filter(item => counts[item] ? true : (counts[item] = 1, false));**
}
console.log(findDuplicates([1, 2, 2, 3, 4, 4, 5]));
// Output: [2, 4]
3. Implement debounce
Question : Write a debounce function that limits the rate a function is called.
Code :
function debounce(func, delay) {
** let timer;**
** return function (...args) {**
** clearTimeout(timer);**
** timer = setTimeout(() => func.apply(this, args), delay);**
** };**
}
const log = debounce(() => console.log('Logged after 1s'), 1000);
log();
4. Reverse a String Recursively
Question : Write a recursive function to reverse a string.
Code :
function reverseString(str) {
** if (str === "") return "";**
** return reverseString(str.slice(1)) + str[0];**
}
console.log(reverseString("hello"));
// Output: "olleh"
5. Check for Palindrome
Question : Write a function to check if a string is a palindrome.
Code :
function isPalindrome(str) {
** const cleaned = str.toLowerCase().replace(/[^a-z]/g, '');**
** return cleaned === cleaned.split('').reverse().join('');**
}
console.log(isPalindrome("A man, a plan, a canal, Panama"));
// Output: true
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