How to replace all occurrences of a character in a string in JavaScript

In this tutorial, we will learn how to replace all occurrences of a character in a string in JavaScript. String references in Javascript are immutable. This means that once a String object is assigned to a String reference(variable), the value of the object cannot be changed.

Replace all occurrences of a character in a string in JavaScript

Variables used in the code

  • str – string
  • searchChar – replaced character
  • replaceChar – replacing character.
let str = "This is a Tutorial in CodeSpeedy"
let searchChar = 'i'
let replaceChar = 'a'

Method 1

This method focuses on replacing all occurrences of a character in a string (case-insensitive).

Inbuilt Functions used 

  • indexOf() – returns the index of the substring in a string.
  • slice() – returns the substring of the string.
  • toLowerCase() – returns the lowercase of the string.
  • toUpperCase() – returns the uppercase of the string.

Here we are finding the index of searchChar in the string str. while the index is not -1, then the searchChar is in the string(str) and we are replacing the character with replaceChar, else we will return the same string str.

function ReplaceAll(str,searchChar,replaceChar){
    while(str.toLowerCase().indexOf(searchChar.toLowerCase())!== -1){
        let index = str.toLowerCase().indexOf(searchChar.toLowerCase())
        if(str[index] === str[index].toUpperCase()){
    	    str = str.slice(0,index)+replaceChar.toUpperCase()+str.slice(index+1,)
        }
        else{
    	    str = str.slice(0,index)+replaceChar.toLowerCase()+str.slice(index+1,)
        }
    }
    return str;
}

Method 2

This method focuses on replacing all occurrences of a character in a string (case-sensitive).

Inbuilt Functions used

  • split() – splits a string into an array of substrings
  • join() – joins an array of substrings to a string.

Here we are splitting the string by searchChar and joining the substring array with replaceChar

function ReplaceAll(str,searchChar,replaceChar){
    let substrings = str.split(searchChar)
    return substrings.join(replaceChar)
}
str = ReplaceAll(str,searchChar,replaceChar) 
console.log(str)

Output

Thas as a Tutoraal an CodeSpeedy

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