Write an audio visualizer from scratch with vanilla JavaScript

Creating an audio visualizer using vanilla JavaScript involves utilizing the inbuilt browser Canvas and Web Audio APIs to transform audio data into dynamic visual bar charts. The process begins with setting up a basic HTML document containing canvas and audio elements and then configuring a development server to address CORS issues. Using the Canvas API, developers can draw 2D graphics on a webpage, while the Web Audio API helps process and play audio files directly in the browser, extracting raw data necessary for visualizations. The tutorial guides through initializing the canvas and audio resources, setting up the Web Audio API variables, and calculating the visualizer’s bar dimensions, followed by animating the bars to create a basic visualizer. Enhancements include adding color, resizing bars for better aesthetics, and improving performance by offloading heavy operations to background threads using Web Workers and OffScreenCanvas. This approach ensures the visualizer runs efficiently without affecting the main thread's responsiveness, providing a comprehensive understanding of creating and refining audio visualizers from scratch.