JavaScript string replace() Method

Q: What are the parameters used in the replace() method?

The replace() method takes two parameters: 1. value1: This can be either a substring to search for or a regular expression to find the match in the string. 2. value2: This is the string that will replace the content matched by value1.

Last Updated : 26 Jun, 2024

JavaScript replace() method is used for manipulating strings. It allows you to search for a specific part of a string, called a substring, and then replace it with another substring.

What’s great is that this method doesn’t alter the original string, making it ideal for tasks where you want to maintain the integrity of the original data. Understanding how to use replace() can enhance your ability to work with strings effectively in JavaScript.

Syntax:

str.replace(value1, value2);

Parameters:

value1: is the regular expression that is to be replaced
value2: is a string that will replace the content of the given string.

Return Values:

It returns a new string with replaced items.

Example 1: Below is an example of the string.replace() Method.

let string = 'GeeksForGeeks';
let newstring = string.replace('GeeksForGeeks', 'GfG');
console.log(newstring);

Output

GfG

Explanation:

A string string is assigned the value 'GeeksForGeeks'.
The replace() method is called on string, searching for the substring 'GeeksForGeeks' and replacing it with 'GfG'.
Since the entire string 'GeeksForGeeks' matches, it is replaced with 'GfG'.
The new string 'GfG' is assigned to the variable newstring.
newstring is logged to the console.

Example 2: Here the contents of the string GeeksForGeeks will be replaced with gfg.

 // Assigning a string
 let string = 'GeeksForGeeks is a CS portal';
    
 // Calling replace() method
 let newstring = string.replace(/GeeksForGeeks/, 'gfg');
 
 // Printing replaced string
 console.log(newstring);

Output

gfg is a CS portal

Explanation:

A string string is assigned the value 'GeeksForGeeks is a CS portal'.
The replace() method is called on string, using a regular expression to match the substring 'GeeksForGeeks' and replace it with 'gfg'.
The first occurrence of 'GeeksForGeeks' in the string is replaced with 'gfg'.
The modified string is assigned to the variable newstring.
The replaced string newstring is logged to the console.

Example 3: Below is an example of the string.replace() Method.

// Taking a regular expression
let re = /GeeksForGeeks/;

// Taking a string as input
let string = 'GeeksForGeeks is a CS portal';

// Calling replace() method to replace
// GeeksForGeeks from string with gfg
let newstring = string.replace(re, 'gfg');

// Printing new string with replaced items
console.log(newstring);

Output

gfg is a CS portal

Explanation:

A regular expression re is defined to match the substring 'GeeksForGeeks'.

A string string is assigned the value 'GeeksForGeeks is a CS portal'.
The replace() method is called on string, using the regular expression re to match the substring 'GeeksForGeeks' and replace it with 'gfg'.
The first occurrence of 'GeeksForGeeks' in the string is replaced with 'gfg'.
The modified string is assigned to the variable newstring.
The replaced string newstring is logged to the console.

We can also replace the same words at multiple places in a string. It is known as a global replacement.

Example 4: This example explains replacing of various similar words in a string.

// Assigning a string
let string = 'GeeksForGeeks is a CS portal.' +
    'In GeeksForGeeks we can learn multiple languages.' +
    'geeksForGeeks is a great place.';

// Calling replace() method
let newstring = string.replace(/GeeksForGeeks/g, 'Gfg');

// Printing replaced string
console.log(newstring);

Output

Gfg is a CS portal.In Gfg we can learn multiple languages.geeksForGeeks is a great place.

Explanation:

A multi-line string string is assigned with multiple occurrences of the substring 'GeeksForGeeks'.

The replace() method is called on string, using a regular expression with the global flag (/g) to match all occurrences of the substring 'GeeksForGeeks' case-sensitively and replacing them with 'Gfg'.
All occurrences of 'GeeksForGeeks' in the string are replaced with 'Gfg'.
The modified string is assigned to the variable newstring.
The replaced string newstring is logged to the console.

Supported Browsers:

Google Chrome 1 and above
Edge 12 and above
Firefox 1 and above
Opera 4 and above
Safari 1 and above

JavaScript String replace() method- FAQS

What is the replace() method in JavaScript and how does it work?

The replace() method in JavaScript is used for manipulating strings. It allows you to search for a specific part of a string, known as a substring, and replace it with another substring. This method returns a new string with the specified replacements and does not alter the original string. This functionality is particularly useful for tasks that require string modifications without affecting the original data.

What are the parameters used in the replace() method?

The replace() method takes two parameters:

1. value1: This can be either a substring to search for or a regular expression to find the match in the string.

2. value2: This is the string that will replace the content matched by value1.

What is the return value of the replace() method?

The replace() method returns a new string where the specified value1 (substring or regular expression match) is replaced with value2. If no matches are found, the original string is returned unchanged.

How does the replace() method handle regular expressions?

When a regular expression is passed as the first parameter ( value1 ), the replace() method can leverage advanced pattern matching capabilities. The regular expression can include flags such as g for global replacements, which replace all occurrences in the string, and i for case-insensitive matches, among others. This allows for more powerful and flexible string manipulation compared to simple substring replacement.

How can you replace all occurrences of a substring in JavaScript?

To replace all occurrences of a substring in JavaScript, you can use the replace() method with a global regular expression (/pattern/g). This instructs the replace() method to find and replace all matches in the string, not just the first one. For example, using /substring/g as the first parameter will ensure that every instance of substring in the string is replaced.