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How to Build a QR Code Generator in JavaScript (Full Code)

Building a client-side QR generator in pure JavaScript is fast, lightweight, and completely private for your web applications.

Core Architectural Steps

  1. Mathematical Encoding Core: Convert text input into byte arrays and calculate Galois Field GF(256) Reed-Solomon parity codewords.
  2. Bit Matrix Layout: Place position finders, timing patterns, and mask evaluation onto a 2D matrix.
  3. HTML5 Canvas Rendering: Loop through dark modules and draw squares, rounded pills, or circular dots onto canvas contexts.
  4. Export: Use canvas.toDataURL('image/png') for instant 1-click downloads.