Strings

Question 1

What is a string in JavaScript?

Answer 1

A sequence of characters used to represent text, enclosed in single or double quotes.

Question 2

How do you find the length of a string?

Answer 2

Use the .length property. Example: let size = str.length;

Question 3

How do you convert a string to uppercase?

Answer 3

Use .toUpperCase(). Example: str.toUpperCase();

Question 4

How do you convert a string to lowercase?

Answer 4

Use .toLowerCase(). Example: str.toLowerCase();

Question 5

How do you extract a portion of a string using indices?

Answer 5

Use .slice(start, end). Example: str.slice(0, 5);

Question 6

How do you replace part of a string?

Answer 6

Use .replace(searchValue, newValue). Example: str.replace('old', 'new');

Question 7

How do you split a string into an array?

Answer 7

Use .split(separator). Example: 'a,b,c'.split(','); returns ['a', 'b', 'c']

Question 8

How do you join an array into a string?

Answer 8

Use .join(separator). Example: ['a', 'b', 'c'].join('-'); returns 'a-b-c'

Question 9

How do you remove whitespace from both ends of a string?

Answer 9

Use .trim(). Example: ' text '.trim();

Question 10

How do you check if a string includes a substring?

Answer 10

Use .includes(substring). Example: str.includes('word');

Question 11

How do you find the index of a substring?

Answer 11

Use .indexOf(substring). Example: str.indexOf('word'); returns index or -1.

Question 12

How do you repeat a string multiple times?

Answer 12

Use .repeat(count). Example: 'ha'.repeat(3); returns 'hahaha'.

Question 13

How do you check if a string starts with a substring?

Answer 13

Use .startsWith(substring). Example: str.startsWith('Hi');

Question 14

How do you check if a string ends with a substring?

Answer 14

Use .endsWith(substring). Example: str.endsWith('end');

Question 15

How do you concatenate two strings?

Answer 15

Use + or .concat(). Example: 'Hello' + ' World' or 'Hello'.concat(' World');

Question 16

How do you convert other data types to a string?

Answer 16

Use String(value) or .toString(). Example: String(123);

Question 17

How do you pad a string to a certain length at the start?

Answer 17

Use .padStart(targetLength, padString). Example: '5'.padStart(3, '0'); → '005'

Question 18

How do you pad a string to a certain length at the end?

Answer 18

Use .padEnd(targetLength, padString). Example: '5'.padEnd(3, '0'); → '500'

Question 19

How do you get a character at a specific index?

Answer 19

Use .charAt(index). Example: 'Hello'.charAt(1); → 'e'

Question 20

How do you access a character using bracket notation?

Answer 20

Use str[index]. Example: 'Hello'[1]; → 'e'

Question 21

What is the difference between slice, substring, and substr?

Answer 21

.slice() and .substring() are similar, but .substr() takes length instead of end index and is deprecated.

Question 22

How do you check if two strings are equal?

Answer 22

Use === for strict comparison. Example: 'abc' === 'abc';

Question 23

How do you escape special characters in a string?

Answer 23

Use backslash \. Example: 'It\'s ok';

Question 24

How do you create a template literal?

Answer 24

Use backticks ` and ${} for interpolation. Example: `Hello ${name}`.

Question 25

How do you match a pattern in a string using regex?

Answer 25

Use `.match(regex)`. Example: `'hello'.match(/h/);`