img-src-placeholder

Replace src=# in <img> tags of HTML files with an inline Base64 data URL of a transparent 1 pixel image (CLI tool designed for use in npm package.json scripts)

img-src-placeholder solves the trickly little problem that valid HTML requires that all <img> tags have a src attribute even if your web application sets the src attribute dynamically.

This tool transforms:

<img src=# alt=avatar>

into:

<img src="data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSIxIiBoZWlnaHQ9IjEiPjwvc3ZnPg=="
   alt=avatar>

A) Setup

Install package for node:

$ npm install --save-dev img-src-placeholder

B) Usage

1. npm package.json scripts

Run img-src-placeholder from the "scripts" section of your package.json file.

Parameters:

• The first parameter is the source folder or file.
• The second parameter is the target folder.

Example package.json scripts:

   "scripts": {
      "stage-web": "img-src-placeholder src/web build/website",
   },

2. Command-line npx

Example terminal commands:

$ npm install --save-dev img-src-placeholder
$ npx img-src-placeholder src/web ext=.html docs/api-manual

You can also install img-src-placeholder globally (--global) and then run it anywhere directly from the terminal.

3. CLI flags

Command-line flags:

Flag	Description	Value
--cd	Change working directory before starting search.	string
--ext	Filter files by file extension, such as .html. Use a comma to specify multiple extensions.	string
--note	Place to add a comment only for humans.	string
--quiet	Suppress informational messages.	N/A
--summary	Only print out the single line summary message.	N/A

The default value for --ext is: ".html,.htm,.php,.aspx,.asp,.jsp"

4. Example CLI usage

Examples:

• img-src-placeholder src/web build/website
  Recursively copies all HTML files in the src/web folder to the build/website folder and replaces the "hash" placeholder image sources with an inline data URL for a transparent 1 pixel image.

• img-src-placeholder src/web build/website --summary
  Displays the summary but not the individual files copied.

• img-src-placeholder src/web build/website --ext=.php
  Only processes PHP files.

• img-src-placeholder src/web 'build/Website Root' --ext=.php
  Specifies a destination folder that has a space in its name.

Note: Single quotes in commands are normalized so they work cross-platform and avoid the errors often encountered on Microsoft Windows.

C) Application Code

Even though img-src-placeholder is primarily intended for build scripts, the package can be used programmatically in ESM and TypeScript projects.

Example:

import { imgSrcPlaceholder } from 'img-src-placeholder';

const options = { extensions: ['.html'] };
const results = imgSrcPlaceholder.transform('src/web', 'build', options);
console.log('Number of files copied:', results.count);

See the TypeScript Declarations at the top of img-src-placeholder.ts for documentation.

D) Under the Hood

The data URL is created by Base64 encoding a super simple <svg> string:

const onePixelSvg =
   '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1"></svg>';
const dataImage = 'data:image/svg+xml;base64,' +
   Buffer.from(onePixelSvg).toString('base64');

---

CLI Build Tools for package.json

• 🎋 add-dist-header:  Prepend a one-line banner comment (with license notice) to distribution files
• 📄 copy-file-util:  Copy or rename a file with optional package version number
• 📂 copy-folder-util:  Recursively copy files from one folder to another folder
• 🪺 recursive-exec:  Run a command on each file in a folder and its subfolders
• 🔍 img-src-placeholder:  Find and replace strings or template outputs in text files
• 🔢 rev-web-assets:  Revision web asset filenames with cache busting content hash fingerprints
• 🚆 run-scripts-util:  Organize npm package.json scripts into groups of easy to manage commands
• 🚦 w3c-html-validator:  Check the markup validity of HTML files using the W3C validator

Feel free to submit questions at:
github.com/center-key/img-src-placeholder/issues

MIT License