Published
Edited
Jul 6, 2019
1 fork
5 stars
features = {
// build an array of features as they are parsed from the stream
const f = [];
for await (const newFeatures of streamGeoJSONL(url)) {
f.push(...newFeatures);
yield f;
}
}
async function* streamGeoJSONL(url) {
const response = await fetch(url);
const reader = response.body.getReader(); // stream reader
const decoder = new TextDecoder('utf-8'); // for decoding binary stream data into strings
try {
let lineFragment = ''; // incomplete line fragment from previous stream chunk
while (true) {
// get next stream chunk
const { done, value } = await reader.read();
if (!done) {
// decode buffer into string, and split into lines
const lines = decoder.decode(value).split('\n');
// prepend last line fragment from previous to the first new line
lines[0] = lineFragment + lines[0];
// save any line fragment from this chunk for next one
lineFragment = lines.pop();
// parse and return new features
yield lines.map(JSON.parse);
}
else {
break; // done processing stream
}
}
}
finally {
reader.releaseLock(); // release lock on stream
}
}
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