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Experiments with Node.js Generator API - partially requires Node 10.
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/* ========================================= | |
IMPORTS | |
-------------------------------------- */ | |
const fs = require('fs') | |
const { promisify } = require('util') | |
sleep = promisify(setTimeout) | |
/* ========================================= | |
BOOTSTRAP | |
-------------------------------------- */ | |
let lines = '' | |
for (var i = 0; i < 10000; i++) { | |
lines += `Lorem ipsum ${i}\n` | |
} | |
filepath = '/tmp/lorem.txt' | |
fs.writeFileSync(filepath, lines, 'utf8') | |
/* ========================================= | |
GENERATORS | |
-------------------------------------- */ | |
function* loremSync(size = 10) { | |
for (let i = 0; i < size; i++) { | |
yield i | |
} | |
} | |
async function* loremAsync(size = 10, delay = 100) { | |
for (let i = 0; i < size; i++) { | |
await sleep(delay) | |
yield i | |
} | |
} | |
/* ========================================= | |
USAGE: generators | |
-------------------------------------- */ | |
function generatorSync(size = 10) { | |
console.log('\n=================================================') | |
console.log(' GENERATORS 1/2: Sync') | |
console.log('----------------------------------------------') | |
for (const value of loremSync(size)) { | |
console.log(value) | |
} | |
console.log('..............................................\n') | |
} | |
async function generatorAsync(size = 10) { | |
console.log('\n=================================================') | |
console.log(' GENERATORS 2/2: Async') | |
console.log('----------------------------------------------') | |
for await (const value of loremAsync(size)) { | |
console.log(value) | |
} | |
console.log('..............................................\n') | |
} | |
/* ========================================= | |
USAGE: streams | |
-------------------------------------- */ | |
function streamAsyncCallback () { | |
console.log('\n=================================================') | |
console.log(' STREAMS 1/2: Callback') | |
console.log('----------------------------------------------') | |
const stream = fs.createReadStream(filepath, { | |
encoding: 'utf8', // null -> buffers, 'utf8' -> strings with that encoding | |
highWaterMark: 1024, // maximum size of each chunk (buffer or string) | |
}) | |
stream.on('data', (chunk) => { | |
process.stdout.write('<DATA>') | |
process.stdout.write(chunk) | |
}) | |
stream.on('end', async () => { | |
console.log('..............................................\n') | |
// II | |
streamAsyncAwaitGenerator() | |
}) | |
} | |
async function streamAsyncAwaitGenerator () { | |
console.log('\n=================================================') | |
console.log(' STREAMS 2/2: Async Generator') | |
console.log('----------------------------------------------') | |
const stream = fs.createReadStream(filepath, { | |
encoding: 'utf8', // null -> buffers, 'utf8' -> strings with that encoding | |
highWaterMark: 1024 // maximum size of each chunk (buffer or string) | |
}) | |
for await (const chunk of stream) { | |
process.stdout.write('<DATA>') | |
process.stdout.write(chunk) | |
} | |
console.log('..............................................\n') | |
// III + IV | |
generatorSync() | |
generatorAsync() | |
} | |
/* ========================================= | |
MAIN | |
-------------------------------------- */ | |
// I | |
streamAsyncCallback() // NOTE: starts callback chain | |
// streamAsyncAwaitGenerator() | |
// generatorSync() | |
// generatorAsync() |
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