HomeCalculatorsUtilitiesHTML ⇄ JS Converter – Real‑time, Live Conversion

HTML ⇄ JS Real‑time Converter

Paste HTML on the left to get JavaScript (using document.writeln) on the right – and vice versa. Instant, live, no buttons.

HTML to JavaScript

JavaScript to HTML

How to use this tool

HTML → JS: Simply paste or type HTML into the left box under “HTML to JavaScript”. The right box instantly shows the corresponding JavaScript code where each line is wrapped in document.writeln("...");. Double quotes and backslashes inside the HTML are properly escaped.

JS → HTML: Paste JavaScript code that contains document.writeln("..."); lines into the left box under “JavaScript to HTML”. The right box will reconstruct the original HTML by removing the document.writeln wrapper and unescaping the content.

All processing happens locally in your browser – your code never leaves your device. The conversion is live, so you see the result immediately as you type or paste.

How it works (the principle)

The conversion is based on simple string manipulation:

  • HTML → JS: Each line of the HTML input is escaped (backslashes become \\, double quotes become \") and then wrapped in document.writeln("...");. This produces valid JavaScript that, when executed, writes the original HTML to the document.
  • JS → HTML: The tool scans each line for the pattern document.writeln("...");. If matched, the inner content is unescaped (replacing \" with " and \\ with \). Lines that don’t match are returned as‑is, allowing the tool to handle mixed content gracefully.

Who should use it? (target audience & scenarios)

  • Web developers embedding HTML snippets inside JavaScript (e.g., for dynamic content injection, ads, or widgets).
  • WordPress/plugin developers who need to output HTML via JavaScript.
  • Content creators using JavaScript to insert third‑party scripts or banners.
  • Educators and students learning how JavaScript string escaping works.
  • Anyone who needs a quick, reliable, and private converter without installing software.

Frequently Asked Questions

Does the tool support multi‑line HTML?

Yes. The HTML input can contain multiple lines. Each line is converted individually, preserving line breaks. In the JS output, you get a series of document.writeln() statements, each on its own line.

What if my JavaScript code contains document.writeln() statements with single quotes?

The tool expects double quotes inside the parentheses. If your code uses single quotes (e.g., document.writeln('...');), the conversion may not work perfectly. We recommend using double quotes for consistency. A future version may support both.

Is my data safe? Do you store anything?

Absolutely. All conversions are performed locally in your browser. No data is sent to any server, and we do not log or store any of your input. Your privacy is completely protected.

Can I use this tool offline?

Once the page is loaded, the conversion runs entirely in your browser. If you save the page or have it cached, you can use it offline without an internet connection (except for external fonts and ads).

What happens if my JS input doesn’t follow the exact document.writeln("..."); pattern?

Lines that do not match the pattern are passed through unchanged. This means you can include other JavaScript code alongside the writeln statements, and they will be preserved. However, for the HTML reconstruction to work correctly, the relevant lines should follow the pattern.