SARS-CoV-2-Viz/fetch.js

// SARS-CoV-2-Viz
// Animated COVID case count visualization
// Copyright 2022 Edward L. Platt <ed@elplatt.com>

async function fetchWithProgress(url, onProgress) {

    // Make request and get headers
    let response = await fetch(url);
    const reader = response.body.getReader();
    const contentLength = response.headers.get('Content-Length');

    // Receive chunks
    let chunks = [];
    let contentReceived = 0;
    while (true) {
	const {done, value} = await reader.read()
	if (done) { break; }
	chunks.push(value);
	let bytes = value.length;
	contentReceived += bytes;

	// Update progress
	onProgress(contentReceived);
    }

    // Combine chunks and decode
    let contentBytes = new Uint8Array(contentReceived);
    let position = 0;
    chunks.forEach((chunk) => {
	contentBytes.set(chunk, position);
	position += chunk.length;
    });
    let content = new TextDecoder("utf-8").decode(contentBytes);
    return content;
}