JavaScript Strings — Interview Questions & Answers

Ques: What is a String in JavaScript?

Ans: A string is a sequence of characters used to represent text in JavaScript.

Strings are enclosed in quotes — single (' '), double (" "), or backticks ( ).

Example:

let str1 = "Hello";
let str2 = 'World';
let str3 = `Hello World`; // Template literal

Ques: What are the different ways to create a string in JavaScript?

Method	Example	Description
String literal	let a = "Hello";	Most common and simple way
String object	let b = new String("Hello");	Creates a string object (not recommended)

Example:

let str1 = "ChatGPT";
let str2 = new String("ChatGPT");
console.log(typeof str1); // "string"
console.log(typeof str2); // "object"

Ques: How can you find the length of a string?

Ans: Use the .length property.

let text = "JavaScript";
console.log(text.length); // 10

Ques: How can you access individual characters in a string?

Ans: Using index notation or .charAt() method.

let text = "Hello";
console.log(text[0]);      // "H"
console.log(text.charAt(1)); // "e"

Ques: What is Template Literal in JavaScript?

Ans: Template literals (backticks ) allow embedding variables and expressions directly inside strings.

let name = "Alice";
let greet = `Hello, ${name}!`;
console.log(greet); // "Hello, Alice!"

They also support multi-line strings:

let msg = `
This is
a multi-line
string.
`;

Ques: What is the difference between slice(), substring(), and substr()?

Method	Parameters	Negative Index	Example	Output
slice(start, end)	Start, end	Yes	"JavaScript".slice(0,4)	"Java"
substring(start, end)	Start, end	No	"JavaScript".substring(4,10)	"Script"
substr(start, length)	Start, length	Yes	"JavaScript".substr(4,6)	"Script"

Ques: How can you search within a string?

Ans: Use these methods:

"JavaScript".includes("Script"); // true
"JavaScript".startsWith("Java"); // true
"JavaScript".endsWith("Script"); // true

Ques: How can you replace all occurrences of a word in a string?

Ans: Use regular expressions with g flag.

let text = "I like JS and JS";
console.log(text.replace(/JS/g, "JavaScript"));
// Output: "I like JavaScript and JavaScript"

Ques: What is the difference between == and === when comparing strings?

• == compares values only
• === compares values and types

"10" == 10;  // true
"10" === 10; // false

Ques: How to convert a number to a string?

String(100);       // "100"
(100).toString();  // "100"

Ques: How to convert a string to a number?

Number("50");   // 50
parseInt("50"); // 50
parseFloat("50.5"); // 50.5

Ques: How to check if a value is a string?

typeof "hello" === "string"; // true
"hello" instanceof String;   // false
new String("hello") instanceof String; // true

Ques: What are escape characters in strings?

Ans: Special characters preceded by a backslash (\\).

Escape	Meaning	Example
\\'	Single quote	'It\\'s fine'
\\"	Double quote	"He said \\"Hello\\""
\\\\	Backslash	"C:\\\\User\\\\Docs"
\\n	New line	"Hello\\nWorld"
\\t	Tab space	"Hello\\tWorld"

Ques: Can strings be modified after creation?

Ans: No, Strings in JavaScript are immutable. Any modification creates a new string.

let str = "Hello";
str[0] = "Y";
console.log(str); // "Hello" (unchanged)

Ques: How can you reverse a string in JavaScript?

Ans: Convert it to an array → reverse → join back:

let str = "hello";
let rev = str.split("").reverse().join("");
console.log(rev); // "olleh"

Ques: How to count occurrences of a character in a string?

let text = "banana";
let count = text.split("a").length - 1;
console.log(count); // 3