Replace all Occurrences of a Substring in a String in JavaScript
Last Updated :
20 Feb, 2024
In Javascript, a string is a sequence of characters represented with quotation marks. We are given a string and we need to replace all occurrences of a substring from the given string.
Using the replace() method with regular expression
- First, declare a string variable str with the value “GeeksforGEEKS”.
- Now, declare a substring variable with the value “GEEKS” to search for and replace.
- Use the replace method with a regular expression to globally replace all instances of the substring with the replacement value “geeks”.
- It logs the result which will be “Geeks For geeks “.
Example: The below code will explain the use of replace() method with regular expression.
Javascript
let str = "GeeksforGEEKS" ;
let substring = "GEEKS" ;
let replacement = "Geeks" ;
console.log( "Before replacement: " , str)
let finalResult =
str.replace( new RegExp(substring, "g" ),
replacement);
console.log( "After Replacement: " , finalResult);
|
Output
Before replacement: GeeksforGEEKS
After Replacement: GeeksforGeeks
Using indexOf() and slice() methods
- The indexOf() method finds the index of the first occurrence of the substring.
- If the index is greater than or equal to 0 (found a match), it slices the string before and after the match and inserts the replacement.
- It recursively calls itself to keep replacing all other matches.
- It returns the final string after replacing all matches.
Example: The below code will explain the use of the indexOf() and slice() methods to replace all occurences of a substring.
Javascript
function replaceAll(str, substring, replacement) {
let index = str.indexOf(substring);
if (index >= 0) {
str =
str.slice(0, index) + replacement +
str.slice(index + substring.length);
str = replaceAll(str, substring, replacement);
}
return str;
}
const str = "GeeksforGEEKS" ;
const subStr = "GEEKS" ;
const replacement = "Geeks" ;
console.log( "Before replacement: " , str)
let finalResult =
replaceAll(str, subStr, replacement);
console.log( "After Replacement: " , finalResult);
|
Output
Before replacement: GeeksforGEEKS
After Replacement: GeeksforGeeks
Using replaceAll() method
- Declare a constant str variable with the initial string “GeeksforGEEKS”.
- Now, use the String.replaceAll() method to replace all occurrences of “GEEKS” in the str with “Geeks”, assigning the result to finalResult and logging it to the console.
Example: The below code is practical implementation of the above-discussed approach.
Javascript
const str = "GeeksforGEEKS" ;
const finalResult =
str.replaceAll( "GEEKS" , "Geeks" );
console.log( "Before replacement: " , str)
console.log( "After Replacement: " , finalResult);
|
Output
Before replacement: GeeksforGEEKS
After Replacement: GeeksforGeeks
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