This guide will help you learn how to trim a String to N characters in JavaScript by using the substring()
, substr()
, and slice()
functions. It’s helpful for you, let’s read it right now.
Trim a string to N characters in JavaScript
The idea to trim a string to N characters in Javascript is that we need to pass the start index and the end index of that string or the length of it to three functions below, and you can learn more about these functions here.
- substring(start, end)
- substr(start, length)
- slice(start, end)
Parameters:
- start: the starting position to extract (required).
- end: the end position (optional).
- length: the length of the substring to be taken from the starting position (optional).
Using substring() method
The parameters passed to the substring()
function must always be greater than 0.
Code sample:
let string = "Welcome to LearnShareIT"; let trimString = string.substring(3, 10); document.write(trimString);
Output
come to
Using substr()
method
Using substr()
method is a simple way to trim a string to N characters in JavaScript. Look at the following example to understand more.
Code sample:
let string = "Welcome to LearnShareIT"; let trimString = string.substr(0, 7); document.write(trimString);
Output
Welcome
If you pass the start parameter as a negative number, it will count from the end up, and the length parameter must always be positive.
Code sample:
let string = "Welcome to LearnShareIT"; let trimString = string.substr(-12, 12); document.write(trimString);
Output
LearnShareIT
Using slice()
method
Code sample:
let string = "Welcome to LearnShareIT"; let trimString = string.slice(8, 16); document.write(trimString);
Output
to Learn
If the input parameter is a negative number, it will count backwards, meaning it will count from the bottom up, like this code.
Code sample:
let string = "Welcome to LearnShareIT"; let trimString = string.slice(-12, 23); document.write(trimString);
Output
LearnShareIT
If you pass only the first parameter, the slice() method will automatically interpret the end position as the last position.
let string = "Welcome to LearnShareIT"; let trimString = string.slice(3); document.write(trimString);
Output
come to LearnShareIT
Summary
Above, I showed you how to trim a string to N characters in JavaScript using the substring(), substr(), and slice() functions. All three functions have similar ways of doing things, but please pay attention to the special cases of the parameters. I hope they are helpful to you. To better understand the lesson’s content, practice rewriting today’s examples. And let’s learn more about JavaScript in the next lessons here. Have a great day!
Maybe you are interested:
- Check if String contains Special Characters in JavaScript
- How to Replace all dots in a String in JavaScript
- How to Replace Spaces with Underscores in JavaScript

Hi, my name is Joni Smith. My job is a programmer. I love learning programming languages, especially C++, C#, php, javascript, html, css. I want to share them with you. I hope my articles will bring a lot of useful knowledge to you.
Name of the university: HVNH BA
Major: htttql MIS
Programming Languages: C++, C#, php, javascript, html, css