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  3. Right-Trim Characters Off a String in JavaScript or Node.js

Right-Trim Characters Off a String in JavaScript or Node.js

Building a client-side API client comes with some challenges when composing the request’s URL. You typically store a base URL that may come with a trailing slash. The partial request’s URL may start with a leading slash as well. If this happens, you should’t concatenate both strings to a final request URL because you would have a double-slash situation.

This tutorial shows you how to trim characters from the end of a string.

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Trim Characters From the Tail of a String Using JavaScript

Working with strings and URLs can be tricky. Composing a correct URL requires you to implement some handling to ensure you’re not adding two slashes.

For example, a situation you want to avoid is this:

const baseUrl = 'https://api.github.com/'  
const repositoryEndpointUrl = '/users/futurestudio/repos'

const requestUrl = baseUrl + repositoryEndpointUrl  
// ⚡️  https://api.github.com//users/futurestudio/repos
//     -> see the double slash after ".com"

An intuitive solution would be to remove the trailing slash from the base URL. That would work for this example. But you and your team may have different ways of defining the endpoint URLs. You may add a leading slash to the endpoint URL, but your college doesn’t which ends up in a “no-slash” situation 🙈

Let’s say you have the convention of always starting your endpoint URLs with a leading slash. Then you need to ensure the base URL doesn’t have a trailing slash. You should still add functionality to remove a possibly existing trailing slash from the base URL.

Here’s a sample function removing whitespaces or provided characters from the end of a string:

/**
 * Removes whitespaces from the tail of the string when
 * no argument value is present. It trims the provided `character`
 * from the end of the string if you pass along a value.
 *
 * @param {String} character
 *
 * @returns {Boolean}
 */
function rtrim (string, character) {  
  character = character || ''

  if (!character) {
    return string.trimEnd()
  }

  if (!string.endsWith(character)) {
    return string
  }

  while (string.lastIndexOf(character) > -1) {
    const end = string.lastIndexOf(character)

    string = string.slice(0, end)
  }

  return string
}

You can use the rtrimutility method like this:

rtrim('Future Studio  ')  
// 'Future Studio'

rtrim('  Future Studio  ')  
// '  Future Studio'

rtrim('https://api.github.com', '/')  
// 'https://api.github.com'

rtrim('https://api.github.com/', '/')  
// 'https://api.github.com'

rtrim('https://api.github.com///', '/')  
// 'https://api.github.com'

Use the @supercharge/strings Package

I’m the maintainer of the @supercharge/strings package providing convenient string utilities. The @supercharge/strings package comes with a handy Str#rtrim(characters?) method.

This rtrim method removes whitespaces from the end of a given string or the provided characters:

import { Str } from '@supercharge/string'

Str('Future Studio  ').rtrim().get()  
// 'Future Studio'

Str('  Future Studio  ').rtrim().get()  
// '  Future Studio'

Str('https://api.github.com///').rtrim('/').get()  
// 'https://api.github.com'

Enjoy removing characters from the tail of a string!

Mentioned Resources

Marcus Pöhls

Marcus is a fullstack JS developer. He’s passionate about the hapi framework for Node.js and loves to build web apps and APIs. Creator of Futureflix and the “learn hapi” learning path.

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