Javascript String

Introduction

In JavaScript, a string is a sequence of characters used to represent text. Strings are one of the fundamental data types in JavaScript and are commonly used to store and manipulate textual data.

String can be enclosed in Single Quotes like ‘john’ or Double Quotes like “john” or backtics (which came into ES6) like `john`.

What is a JavaScript String?

A String in JavaScript is a sequence of characters enclosed inside quotes. It can contain letters, numbers, symbols, and spaces.

JavaScript supports three ways to create strings:

1. Single quotes (”)
2. Double quotes (“”)
3. Template literals ( )

Syntax of JavaScript String

let variableName = 'value';
//or
let variableName = "value";
//or
let variableName = `value`;

Example:

let name = 'John';
let city = "Delhi";
let message = `Welcome to JavaScript`;

Creating Strings in JavaScript

You can create a string in the following ways.

1. Using Double Quotes

let name = "John";
console.log(name);

Output:

2. Using Single Quotes

let city = 'Delhi';
console.log(city);

Output:

3. Using Template Literals

Template literals support variables and multiline strings.

let name = "John";
console.log(`Hello ${name}`);

Output:

4. Using String() Method

You can create a string through the String() function.

var age=35;
var age_string=String(age);  
console.log(age_string);  // Output:- "35"

Output:

5.  Using toString() Method

toString() is used to convert data into a string.

var age =35;
var age_string=age.toString(); 
console.log(age_string);  // Output:- "35"

Output:

6. Using a new keyword

Creating a String Object through the new keyword, and it behaves like an Object.

var string_object = new String("John");
console.log(string_object);         
console.log(string_object.toString()); 
console.log(string_object.valueOf()); 

Output:

JavaScript String Methods

Strings provide built-in methods for manipulating text.

1. length Property

It returns the total number of characters.

let text = "John";
console.log(text.length);

Output:

2. toUpperCase() Method

It converts text into uppercase.

let name = "john";
console.log(name.toUpperCase());

Output:

3. toLowerCase() Method

It converts text into lowercase.

let city = "DELHI";
console.log(city.toLowerCase());

Output:

4. trim() Method

It removes extra spaces.

let str = "   Hello   ";
console.log(str.trim());

Output:

5. includes() Method

It checks whether text exists.

let msg = "Learn JavaScript";
console.log(msg.includes("Java"));

Output:

6. replace() Method

It replaces characters or words.

let text = "I like Java";
console.log(text.replace("Java","JavaScript"));

Output:

7. slice() Method

It extracts part of a string.

let word = "Hello World";
console.log(word.slice(0,4));

Output:

8. split() Method

It converts a string into an array.

let fruits = "Apple,Banana,Mango";
console.log(fruits.split(","));

Output:

How to Concatenate a String

Combining multiple strings is called concatenation.

1. Using + to add Multiple Strings

Example:

let firstName = "John";
let lastName = "Taylor";
console.log(firstName + " " + lastName);

Output:

2. Using template literals:

let first = "John";
let last = "Taylor";
console.log(`${first} ${last}`);

Output:

Escape Characters in Strings

Escape characters allow special formatting.

Example:

let text = "He said \"Hello\"";
console.log(text);

Output:

Common escape characters:

Example of JavaScript String

Example 1: Display User Name

let username = "John";
console.log("Welcome " + username);

Output:

Example 2: Find String Length

let course = "JavaScript";
console.log(course.length);

Output:

Example 3: Convert Uppercase

let name = "John";
console.log(name.toUpperCase());

Output:

String can be enclosed in Single Quotes like ‘john’ or Double Quotes like “john” or backtics (which came into ES6) like `john`.

var first_name ='John';
var last_name="Taylor";
var email=`john@abc.com`;

Note:- backtics is basically used to combined variable value and strings.

Example:- Now you add first_name and last_name along with Hello string.

var full_name=`Hello ${first_name} ${last_name}`;
console.log(full_name);  // Output:- John Taylor

Create a String:-

1) String():- You can create string through String function.

var age=35;
var age_string=String(age);  
console.log(age_string);  // Output:- "35"

var bool =true;
var bool_string=String(bool) // Output:- "true"

2) toString():- toString() is used to convert data into string.

var age =35;
var age_string=age.toString(); // Output "35";

var bool =true;
var bool_string=bool.toString() // Output:- "true"

3) creating a String Object through new keyword and it behaves like Object

var string_object = new String("John");
console.log(typeof string_object); //output:- "object" 

Concat two or more strings:- 1) You can concat the two string through + sign

var first_name="John";
var last_name="Taylor";
document.write(first_name + last_name); //Output:- JohnTaylor
document.write(first_name +' '+last_name); //Output:- John Taylor

Try it Yourself

2) You can concat strings through concat() keyword.

var first_name="John";
var last_name="Taylor";
document.write(first_name.concat(last_name)); //Output:- JohnTaylor

Try it Yourself

3) Concat string through backtics

var first_name="John";
var last_name="Taylor";
document.write(`${first_name} ${last_name}`); //Output:- John Taylor

Try it Yourself

trim() method:- this method is used to trim the white space from the string.

var name=" John ";
console.log(name.trim());  //Output:- John

split() method:- It is used to split a string into Array

var str="John went to college";
var str_arr=str.split(" ");
document.write(str_arr[0]);   // Output:- John
document.write(str_arr[1]);   // Output:- went
document.write(str_arr[2]);   // Output:- to
document.write(str_arr[3]);   // Output:- college

Try it Yourself

join() method:- It is used convert Array into String

arr=["John", "went", "to", "college"];
arr_to_string= arr.join("-");
document.write(arr_to_string);  // Output:- John-went-to-college

Try it Yourself

Reverse a string:-

var str="John Taylor"
let rev_string= str.split('').reverse().join('');
document.write(rev_string);  // Output:- rolyaT nhoJ

Try it Yourself

Javascript String – Interview Questions

Javascript String – Objective Questions (MCQs)