TypeScript icon, indicating that this package has built-in type declarations

1.1.1 • Public • Published

comment-mark Latest version Monthly downloads Install size Bundle size

Use comment-mark to insert dynamic content in Markdown/HTML:

  1. Prepare Markdown content with placeholders

    let markdownString = `
    ## Last updated
    <!-- lastUpdated:start --><!-- lastUpdated:end -->
  2. Apply comment-mark to insert data into the placeholders

    markdownString = commentMark(markdownString, {
        lastUpdated: (new Date()).toISOString()
  3. Done!

    ## Last updated
    <!-- lastUpdated:start -->2021-02-01T02:48:03.797Z<!-- lastUpdated:end -->

🚀 Install

npm i comment-mark

🙋‍♂️ Why?

Most approaches to interpolating dynamic data into a Markdown file involves maintaining a Markdown template as the source, and a build step that produces the actual Markdown file.

Comment-mark lets you use a single Markdown file as both the template and distribution file by using persistent placeholders.

Real examples:

👨🏻‍🏫 Quick demo

The following example demonstrates how comment-mark can be used to interpolate a list of the project's Git contributors to

const fs = require('fs')
const { execSync } = require('child_process')
const commentMark = require('comment-mark')

let mdStr = fs.readFileSync('./')

mdStr = commentMark(mdStr, {
    contributors: execSync('git shortlog -se HEAD -- .').toString()

fs.writeFileSync('./', mdStr)


# Welcome to my project

## Contributors
<!-- contributors:start --><!-- contributors:end -->


# Welcome to my project

## Contributors
<!-- contributors:start -->
    17	John Doe <>
<!-- contributors:end -->

⚙️ Options

commentMark(contentStr, data)

  • contentStr <string> The input string
  • data - <{[key: string]: string}> Key-value pairs to inject into the string

Output: The input string with the key-value pairs from data interpolated in it

💁‍♀️ FAQ

Why use HTML comments?

This is primarily designed for Markdown files, where basic HTML is typically supported. HTML comment pairs serve as a convenient placeholder to insert a string in between.

Why are there pairs of HTML comments instead of just one placeholder?

So that the interpolation positions are preserved throughout interpolations.

If there's only one placeholder that gets replaced during interpolation, the placeholder will be lost after the first interpolation. This kind of approach will require a separation of "source" and "distribution" files.

Package Sidebar


Weekly Downloads






Unpacked Size

7.02 kB

Total Files


Last publish


  • hirokiosame