JavaScript Viewer

Paste JavaScript and get an instant colour-coded view — keywords, strings, comments, and numbers highlighted for easy reading.

Last updated: May 29, 2026

JavaScript Source

20 lines · 734 chars

// Async data fetcher with retry logic
async function fetchWithRetry(url, maxRetries = 3) {
  for (let attempt = 1; attempt <= maxRetries; attempt++) {
    try {
      const response = await fetch(url);
      if (!response.ok) throw new Error(`HTTP ${response.status}`);
      return await response.json();
    } catch (error) {
      if (attempt === maxRetries) throw error;
      const delay = Math.pow(2, attempt) * 100;
      await new Promise(resolve => setTimeout(resolve, delay));
      console.warn(`Retry ${attempt}/${maxRetries} after ${delay}ms`);
    }
  }
}

// Example usage
fetchWithRetry("https://api.example.com/data")
  .then(data => console.log("Got:", data))
  .catch(err => console.error("Failed:", err.message));

Client-Side Processing

Input Data Stays on Device

Instant Local Execution

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What is JavaScript Viewer?

JavaScript Viewer renders JavaScript source code with syntax highlighting using a client-side tokeniser. Keywords like function, const, return, and async are highlighted in blue; string literals in orange; comments in green; and numeric literals in light green. The Preview tab shows the dark-theme highlighted output; the HTML tab shows the raw highlighted HTML you can embed in a blog post or documentation page.

How to Use JavaScript Viewer

Paste JavaScript into the input.

The highlighted preview updates instantly.

Switch to HTML tab to get the embeddable highlighted markup.

Copy either the plain code or the highlighted HTML.

Common Use Cases

Previewing how a code snippet will look before adding it to a blog post.
Generating syntax-highlighted HTML to embed in documentation or a CMS.
Reading unfamiliar JavaScript code with colour-coded structure for faster understanding.
Sharing a readable, colour-coded version of a snippet in a presentation or README.

Example Input and Output

A JavaScript function is displayed with keyword and string highlighting.

JavaScript source

const greet = name => `Hello, ${name}!`;

Highlighted preview

<span style="color:#569cd6">const</span> greet = name => <span style="color:#ce9178">`Hello, ${name}!`</span>;

Privacy

JavaScript code is processed locally in the browser and is never uploaded.

Frequently Asked Questions

Can I use the highlighted HTML in my blog?

Yes. Switch to the HTML tab and copy the output. It uses inline styles, so it works without any external CSS or JavaScript dependencies.

Does it support TypeScript?

The highlighter applies JavaScript tokenisation rules. TypeScript-specific syntax (type annotations, interfaces) will largely be highlighted correctly since TypeScript is a superset of JavaScript.

Is my code uploaded anywhere?

No. Highlighting runs entirely in your browser.

What colour theme does it use?

The preview uses a VS Code Dark+ inspired theme with a #1e1e1e background. The HTML export includes these colours as inline styles.