Replace all Occurrences of a Substring in a String in JavaScript

Given a String, the task is to replace all occurrences of a substring using JavaScript. The basic method to replace all substring of a string is by using string.replaceAll() method.

The string.replaceAll() method is used to search and replace all the matching substrings with a new string. We can use the regular expression as a pattern to find all the matching substrings.

Syntax

string.replaceAll(sunstring, replacement); 

let str = "GEEKSforGEEKS";
let substring = "GEEKS";
let replacement = "Geeks";

// Replace all occurrences of substring
let updatedStr = str.replaceAll(substring, replacement);

// Updated string
console.log("Updated String:", updatedStr);

Updated String: GeeksforGeeks

Using String replace() Method with Regular Expression

The string replace() method is used to search and replace a substings with a new string. We can use the regular expression as a pattern to find all the matching substrings.

Syntax

string.replace(substring, replacement); 

let str = "GEEKSforGEEKS";
let substring = "GEEKS";
let replacement = "Geeks";

let updatedStr = str.replace(new RegExp(substring, "g"), replacement);

// Updated string
console.log("Updated String:", updatedStr);

Updated String: GeeksforGeeks

Using indexOf() and slice() Methods

The indexOf() method finds the index of the first occurrence of the substring. Next, we can break the string from that index using str.slice() and insert the replacement string to get the required output.

str.indexOf(searchValue, startIndex);
string.slice(startingIndex, endingIndex);

let str = "GEEKSforGEEKS";
let substring = "GEEKS";
let replacement = "Geeks";

while (str.indexOf(substring) !== -1) {
    let index = str.indexOf(substring);
    str = str.slice(0, index) + replacement + str.slice(index + substring.length);
}

// Updated string
console.log("Updated String:", str);

Updated String: GeeksforGeeks