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JavaScript Strings - GeeksforGeeks

A JavaScript String is a sequence of characters, typically used to represent text.

• In JavaScript, there is no character type (Similar to Python and different from C, C++ and Java), so a single character string is used when we need a character.
• Like Java and Python, strings in JavaScript are immutable.

We can either use a single quote or a double quote to create a string. We can use either of the two, but it is recommended to be consistent with your choice throughout your code.

// Using Single Quote
let s1 = 'abcd';
console.log(s1);

// Using Double Quote
let s2 = "abcd";
console.log(s2);

Recommended Links

• Interesting Facts about JS Strings
• JS String Reference
• JS String Exercise

The new String() constructor creates a string object instead of a primitive string. It is generally not recommended because it can cause unexpected behavior in comparisons

let s = new String('abcd');
console.log(s);

You can create strings using Template Literals. Template literals allow you to embed expressions within backticks (`) for dynamic string creation, making it more readable and versatile.

let s1 = 'gfg';
let s2 = `You are learning from ${s1}`;

console.log(s2);

You are learning from gfg

You can create an empty string by assigning either single or double quotes with no characters in between.

let s1 = '';
let s2 = "";

console.log(s1);
console.log(s2);

Since the strings are empty, console.log will print two blank lines.

You can create a multiline string using backticks (``) with template literals. The backticks allows you to span the string across multiple lines, preserving the line breaks within the string.

let s = `
    This is a
    multiline
    string`;

console.log(s);

    This is a
    multiline
    string

1. Finding the length of a String

You can find the length of a string using the length property.

let s = 'JavaScript';
let len = s.length;

console.log("String Length: " + len);

2. String Concatenation

You can combine two or more strings using + Operator.

let s1 = 'Java';
let s2 = 'Script';
let res = s1 + s2;

console.log("Concatenated String: " + res);

Concatenated String: JavaScript

3. Escape Characters

We can use escape characters in string to add single quotes, dual quotes, and backslash.

\' - Inserts a single quote
\" - Inserts a double quote 
\\ - Inserts a backslash

const s1 = "\'GfG\' is a learning portal";
const s2 = "\"GfG\" is a learning portal";
const s3 = "\\GfG\\ is a learning portal";

console.log(s1);
console.log(s2);
console.log(s3);

'GfG' is a learning portal
"GfG" is a learning portal
\GfG\ is a learning portal

4. Breaking Long Strings

Using a backslash (\) to break a long string is not recommended, as it is not supported in strict mode. Instead, use template literals or string concatenation.

const s = "'GeeksforGeeks' is \
a learning portal";

console.log(s);

'GeeksforGeeks' is a learning portal

Note: This method might not be supported on all browsers. A better way to break a string is by using the string addition.

const s = "'GeeksforGeeks' is a"
    + " learning portal";

console.log(s);

'GeeksforGeeks' is a learning portal

5. Find Substring of a String

We can extract a portion of a string using the substring() method.

let s1 = 'JavaScript Tutorial';
let s2 = s1.substring(0, 10);

console.log(s2);

6. Convert String to Uppercase and Lowercase

Convert a string to uppercase and lowercase using toUpperCase() and toLowerCase() methods.

let s = 'JavaScript';
let uCase = s.toUpperCase();
let lCase = s.toLowerCase();

console.log(uCase);
console.log(lCase);

JAVASCRIPT
javascript

7. String Search in JavaScript

Find the first index of a substring within a string using indexOf() method.

let s1 = 'def abc abc';
let i = s1.indexOf('abc');

console.log(i);

8. String Replace in JavaScript

Replace occurrences of a substring using the replace() method. By default, replace() only replaces the first occurrence. To replace all occurrences, use a regular expression with the g flag.

let s1 = 'Learn HTML at GfG and HTML is useful';
let s2 = s1.replace(/HTML/g, 'JavaScript');

console.log(s2);

Learn JavaScript at GfG and JavaScript is useful

9. Trimming Whitespace from String

Remove leading and trailing whitespaces using trim() method.

let s1 = '    Learn JavaScript       ';
let s2 = s1.trim();

console.log(s2);

10. Access Characters from String

Access individual characters in a string using bracket notation and charAt() method.

let s1 = 'Learn JavaScript';
let s2 = s1[6];
console.log(s2);

s2 = s1.charAt(6);
console.log(s2);

11. String Comparison in JavaScript

There are some inbuilt methods that can be used to compare strings such as the equality operator and another like localeCompare() method.

let s1 = "Ajay"
let s2 = new String("Ajay");

console.log(s1 == s2);  // true (type coercion)
console.log(s1 === s2); // false (strict comparison)
console.log(s1.localeCompare(s2)); // 0 (means they are equal lexicographically)

Note: The equality operator (==) may return true when comparing a string object with a primitive string due to type coercion. However, === (strict equality) returns false because objects and primitives are different types. The localeCompare() method compares strings lexicographically.

12. Passing JavaScript String as Objects

We can create a JavaScript string using the new keyword.

const str = new String("GeeksforGeeks");

console.log(str);

[String: 'GeeksforGeeks']

No, the string created by the new keyword is an object and is not the same as normal strings.

const str1 = new String("GeeksforGeeks");
const str2 = "GeeksforGeeks";

console.log(str1 == str2);
console.log(str1 === str2);

What is a string 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 enclosed in single quotes ('), double quotes ("), or backticks (`).

How do you create a string?

You can create a string by enclosing characters in single quotes, double quotes, or backticks.

Examples:

• 'Hello'
• "World"
• `Hello World`

What are template literals?

Template literals are strings enclosed in backticks (`) and allow for embedded expressions using ${expression}. They can span multiple lines and include interpolated variables and expressions.

Example: `Hello, ${name}!`

How do you access characters in a string?

You can access characters in a string using bracket notation and the index of the character. The index starts at 0 for the first character.

Example: str[0]

How do you find the length of a string?

You can find the length of a string using the length property.

Example: str.length

How do you concatenate strings?

You can concatenate strings using the + operator or the concat() method.

Example: str1 + str2 or str1.concat(str2)

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