How to Replace Last 3 Characters of String in Javascript
In this tutorial, you will learn how to replace last 3 characters of string in javascript. A string is built using multiple characters. That means the last 3 characters in a string can be letters, numbers, or special characters. It can also be a combination of letters, numbers, and special characters.
There are numerous ways to replace the last 3 characters of the string. We are going to create a custom function that involves the usage of split()
, join()
, and reverse()
methods as well as for
loop to loop through all characters. Later, we will use replace()
method to replace the last 3 characters with an exclamation mark (!
).
In the following example, we have one global variable that holds a string. Upon click of a button, we will replace the last 3 characters of the string and display the result on the screen. Please have a look over the code example and the steps given below.
HTML & CSS
- We have 3 elements in the HTML file (
div
,button
, andh1
). Thediv
element is just a wrapper for the rest of the elements. - The
innerText
for thebutton
element is“Get”
and for theh1
element, it is“Result”
. - We have done some basic styling using CSS and added the link to our
style.css
stylesheet inside thehead
element. - We have also included our javascript file
script.js
with ascript
tag at the bottom.
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <link rel="stylesheet" href="style.css"> <title>Document</title> </head> <body> <div class="container"> <button>Get</button> <h1>Result</h1> </div> <script src="script.js"></script> </body> </html>
.container { text-align: center; } button { margin-top: 10px; padding: 10px 20px; }
Javascript
- We have selected the
button
element andh1
element using thedocument.querySelector()
method and stored them inbtnGet
andoutput
variables respectively. - We have attached a
click
event listener to thebutton
element. - We have a global variable
myString
which holds a string as its value. - In the event handler function, we are calling the
replaceCharacters()
method and passingmyString
and 3 as parameters. This method will be responsible for replacing the last 3 characters and returning the new string. - In the
replaceCharacters()
method, we are calling thereverseString()
method and passingstr
as a parameter. This method will reverse the string and return it. - We are using
for
loop to loop through all the characters in the string. Inside the loop, we are usingreplace()
method to replace the last 3 characters with an exclamation mark (!
). - The final string is stored in the
newStr
variable. - We are getting out of the loop using the
break
statement after replacing the last 3 characters. - The returned string is stored in the
result
variable and we are displaying theresult
in theh1
element using theinnerText
property.
let btnGet = document.querySelector("button"); let output = document.querySelector("h1"); let myString = "Hello world"; btnGet.addEventListener("click", () => { let result = replaceCharacters(myString, 3); output.innerText = result; }); function replaceCharacters(str, num) { str = reverseString(str); let newStr = str; let count = 0; for (const char of str) { newStr = newStr.replace(char, "!"); count++; if (count == num) { newStr = reverseString(newStr); break; } } return newStr; } function reverseString(str) { return str.split("").reverse().join(""); }