Sanitize your strings in JavaScript like a Rails developer

This article, originally published on Rails Designer, is extracted from the book JavaScript for Rails Developers. Get your copy today. ✌️ Ruby (and Rails) are known for great Developer Experience. Not in the least because of the many little helpers available. JavaScript doesn't have most of these unfortunately, but luckily, as a developer, many are easily replicated. Let's look at the API I am looking for: class Editor { async #update(content) { const sanitizedContent = sanitize(content, { trimTrailingWhitespace: true }) const response = await fetch( this.updateUrlValue, { // … body: JSON.stringify({ content: sanitizedContent }) } ) // … } } sanitize(content, { trimTrailingWhitespace: true }) is what I want to implement. You could extend the options with whatever you need: sanitize(content, { trimTrailingWhitespace: true, trimLeadingWhitespace: true, maxConsecutiveNewlines: 2, maxConsecutiveSpaces: 1 // … etc. }) The code for it is quite simple really! Let's create it at: app/javascript/helpers/textSanitizers.js. // app/javascript/helpers/textSanitizers.js class TextSanitizers { } export const sanitize = (content, options = {}) => { return new TextSanitizers(content).process(options) } Above shows that the content is passed as an argument and then very likely set as an instance variable. It also needs a process method. class TextSanitizers { + constructor(content) { + this.content = content + } + process(options = {}) + return this.content.replace(/[ \t]+$/gm, "") + } } Above is all that is needed to sanitize trailing white-spaces from the content. But I want this class to be responsible for many more sanitizations! Let's set it up to be ready for that. class TextSanitizers { + availableCleaners = [ + "trimTrailingWhitespace" + ] constructor(content) { this.content = content } process(options = {}) { - return this.content.replace(/[ \t]+$/gm, "") + return Object.entries(options).reduce((result, [option, value]) => { + return this.availableCleaners.includes(option) ? this[option](result, value) : result + }, this.content) } // private + trimTrailingWhitespace(text) { + return text.replace(/[ \t]+$/gm, "") + } } The process method determines which cleaning operations need to run. When no options are passed, it defaults to an empty object ({}). Then inside the method Object.entries converts the options into an array of key-value pairs: {trimTrailingWhitespace: true} would become: [["trimTrailingWhitespace", true]]. If this seems like a lot, the book JavaScript for Rails Developers has you covered (more sanitization options included)!

Apr 24, 2025 - 18:28

Sanitize your strings in JavaScript like a Rails developer

This article, originally published on Rails Designer, is extracted from the book JavaScript for Rails Developers. Get your copy today. ✌️

Ruby (and Rails) are known for great Developer Experience. Not in the least because of the many little helpers available. JavaScript doesn't have most of these unfortunately, but luckily, as a developer, many are easily replicated. Let's look at the API I am looking for:

class Editor {
  async #update(content) {
    const sanitizedContent = sanitize(content, { trimTrailingWhitespace: true })

    const response = await fetch(
      this.updateUrlValue,
      {
        // …

        body: JSON.stringify({
          content: sanitizedContent
        })
      }
    )

    // …
  }
}

sanitize(content, { trimTrailingWhitespace: true }) is what I want to implement. You could extend the options with whatever you need:

sanitize(content, {
  trimTrailingWhitespace: true,
  trimLeadingWhitespace: true,
  maxConsecutiveNewlines: 2,
  maxConsecutiveSpaces: 1
  // … etc.
})

The code for it is quite simple really! Let's create it at: app/javascript/helpers/textSanitizers.js.

// app/javascript/helpers/textSanitizers.js
class TextSanitizers {
}

export const sanitize = (content, options = {}) => {
  return new TextSanitizers(content).process(options)
}

Above shows that the content is passed as an argument and then very likely set as an instance variable. It also needs a process method.

class TextSanitizers {
+  constructor(content) {
+    this.content = content
+  }

+  process(options = {})
+    return this.content.replace(/[ \t]+$/gm, "")
+  }
}

Above is all that is needed to sanitize trailing white-spaces from the content. But I want this class to be responsible for many more sanitizations! Let's set it up to be ready for that.

class TextSanitizers {
+  availableCleaners = [
+    "trimTrailingWhitespace"
+  ]

  constructor(content) {
    this.content = content
  }

  process(options = {}) {
-   return this.content.replace(/[ \t]+$/gm, "")
+   return Object.entries(options).reduce((result, [option, value]) => {
+     return this.availableCleaners.includes(option) ? this[option](result, value) : result
+   }, this.content)
  }

  // private

+  trimTrailingWhitespace(text) {
+    return text.replace(/[ \t]+$/gm, "")
+  }
}

The process method determines which cleaning operations need to run. When no options are passed, it defaults to an empty object ({}). Then inside the method Object.entries converts the options into an array of key-value pairs: {trimTrailingWhitespace: true} would become: [["trimTrailingWhitespace", true]]. If this seems like a lot, the book JavaScript for Rails Developers has you covered (more sanitization options included)!