Replace all Occurrences of a Substring in a String in JavaScript
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.
Table of Content
- Using replace() method with regular expression
- Using indexOf() and slice() methods
- Using replaceAll() method
Using the replace() method with regular expression
- First, declare a string variable str with the value “BeginnerforBeginner”.
- Now, declare a substring variable with the value “Beginner” 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 “Beginner”.
- It logs the result which will be “Beginner For Beginner “.
Example: The below code will explain the use of replace() method with regular expression.
Javascript
let str = "BeginnerforBeginner" ; let substring = "Beginner" ; let replacement = "Beginner" ; console.log( "Before replacement: " , str) let finalResult = str.replace( new RegExp(substring, "g" ), replacement); console.log( "After Replacement: " , finalResult); |
Output
Before replacement: BeginnerforBeginner After Replacement: BeginnerforBeginner
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 = "BeginnerforBeginner" ; const subStr = "Beginner" ; const replacement = "Beginner" ; console.log( "Before replacement: " , str) let finalResult = replaceAll(str, subStr, replacement); console.log( "After Replacement: " , finalResult); |
Output
Before replacement: BeginnerforBeginner After Replacement: BeginnerforBeginner
Using replaceAll() method
- Declare a constant str variable with the initial string “BeginnerforBeginner”.
- Now, use the String.replaceAll() method to replace all occurrences of “Beginner” in the str with “Beginner”, 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 = "BeginnerforBeginner" ; const finalResult = str.replaceAll( "Beginner" , "Beginner" ); console.log( "Before replacement: " , str) console.log( "After Replacement: " , finalResult); |
Output
Before replacement: BeginnerforBeginner After Replacement: BeginnerforBeginner