31:Td4f,geojsonStream = (response) => { // Copy/pasted from https://github.com/canjs/can-ndjson-stream // For cancellation let isReader let cancellationRequest = false const featuresDepth = 1 let parser let objectDepth = 0 let parsingFeatures = false let commaNeeded = false return new ReadableStream({ start: (controller) => { parser = clarinet.parser() let possibleFeature = '' parser.onopenarray = () => { if (parsingFeatures) { possibleFeature += (commaNeeded ? ',' : '') + '[' } if (objectDepth === featuresDepth) { parsingFeatures = true } commaNeeded = false } parser.onclosearray = () => { if (objectDepth === featuresDepth) { parsingFeatures = false } if (parsingFeatures) { possibleFeature += ']' } commaNeeded = true } parser.onopenobject = (key) => { objectDepth += 1 if (parsingFeatures) { possibleFeature += (commaNeeded ? ',' : '') + `{${JSON.stringify(key)}:` } commaNeeded = false } parser.oncloseobject = () => { objectDepth -= 1 if (parsingFeatures) { possibleFeature += '}' } commaNeeded = true if (objectDepth === 1) { if (possibleFeature.length) { try { const parsedPossibleFeature = JSON.parse(possibleFeature) if (parsedPossibleFeature && parsedPossibleFeature.type && parsedPossibleFeature.type === 'Feature') { controller.enqueue(parsedPossibleFeature) } } catch (err) { console.error(err) console.error('Error while parsing:', possibleFeature) controller.error(err) cancellationRequest = true reader.cancel() } } possibleFeature = '' commaNeeded = false } } parser.onkey = (key) => { if (parsingFeatures) { possibleFeature += (commaNeeded ? ',' : '') + `${JSON.stringify(key)}:` } commaNeeded = false } parser.onvalue = (value) => { if (parsingFeatures) { possibleFeature += (commaNeeded ? ',' : '') + JSON.stringify(value) } commaNeeded = true } parser.onend = () => { // controller.close() } const reader = response.getReader() isReader = reader const decoder = new TextDecoder() reader.read().then(function processResult (result) { if (result.done) { if (cancellationRequest) { // Immediately exit return } controller.close() parser.close() return } const data = decoder.decode(result.value, { stream: true }) parser.write(data) return reader.read().then(processResult) }) }, cancel: (reason) => { console.log('Cancel registered due to ', reason) cancellationRequest = true isReader.cancel() parser.close() } }) }32:[] 2f:{"title":"Streaming GeoJSON","cells":[{"id":0,"value":"md`# Streaming GeoJSON`","pinned":false,"hidden":false,"mode":"ojs"},{"id":1299,"value":"md`Streaming parsing and filtering for GeoJSON features with the [Streams API](https://developer.mozilla.org/en-US/docs/Web/API/Streams_API) and [clarinet](https://github.com/dscape/clarinet).\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":1322,"value":"html`\n \n \n \n \n \n \n \n ${geojson.features.slice(0, 250).map((feature) => html`\n \n \n \n `)}\n \n

Place name	Coordinates
${feature.properties.NAME}	\n \n ${feature.geometry.coordinates.join(', ')}\n \n

\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":1207,"value":"geojson = streamingGeoJSON(url, filter, 250)","pinned":false,"hidden":false,"mode":"ojs"},{"id":1283,"value":"streamingGeoJSON = async function *(url, filter = undefined, yieldEvery = 250) {\n const features = []\n \n const reader = await getGeoJSONStream(url, filter)\n\n let result\n while (!result || !result.done) {\n result = await reader.read()\n const feature = result.value\n \n if (feature && filter(feature)) {\n features.push(feature)\n }\n \n if (features.length % 250 === 0) {\n yield createGeoJSON(features)\n } \n }\n \n yield createGeoJSON(features)\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":1192,"value":"filter = (feature) => feature.properties.ADM0NAME === 'Netherlands'","pinned":false,"hidden":false,"mode":"ojs"},{"id":1168,"value":"// Example URL\nurl = 'https://raw.githubusercontent.com/nvkelso/natural-earth-vector/master/geojson/ne_10m_populated_places.geojson'","pinned":false,"hidden":false,"mode":"ojs"},{"id":40,"value":"getGeoJSONStream = async (url) => {\n const { body } = await fetch(url)\n const reader = geojsonStream(body).getReader()\n return reader\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":37,"value":"$31","pinned":false,"hidden":false,"mode":"ojs"},{"id":1256,"value":"createGeoJSON = (features) => ({\n type: 'FeatureCollection',\n features\n})","pinned":false,"hidden":false,"mode":"ojs"},{"id":1197,"value":"clarinet = require('https://bundle.run/clarinet@0.12.4')","pinned":false,"hidden":false,"mode":"ojs"}],"files":"$W32","stdlib":"1","titling":"auto"}