function parseAndEval(str) // keep only digits, dot, hyphen, and optionally leading/trailing spaces const clean = str.trim(); const parts = clean.split('-'); if (parts.length !== 3) return null; const nums = parts.map(p => parseFloat(p)); if (nums.some(isNaN)) return null; // left‑to‑right subtraction: a - b - c return nums[0] - nums[1] - nums[2];
<a id="downloadBtn" href="assets/2_5m_ruler.pdf" download> <button disabled>Download 2.5 m file</button> </a> x-x-x is equal to 2 5 meter download link
| Tech | Example | |------|---------| | | GET /download?length=2.5 → uses pdfkit to render a 2.5 m ruler PDF, streams it back. | | Python/Flask | @app.route('/download') → builds an SVG/PNG with cairosvg . | | Static CDN | Store the file once ( 2_5m_ruler.pdf ) and serve via CloudFront, Akamai, etc. | function parseAndEval(str) // keep only digits, dot, hyphen,
document.getElementById('validateBtn').addEventListener('click', validate); // optional live validation: // document.getElementById('expr').addEventListener('input', validate); </script> </body> </html> If you need to generate the file on the fly (e.g., a PDF ruler with custom branding), a simple endpoint could be: | document