level-web-stream
Read from an abstract-level database using Web Streams. Compatible with browsers and Node.js.
📌 To instead consume data using Node.js streams, seelevel-read-stream.
Usage
const { EntryStream } = require('level-web-stream')
const { MemoryLevel } = require('memory-level')
const db = new MemoryLevel()
// Write sample data
await db.put('a', '1')
await db.put('b', '2')
await db.put('c', '3')
// Create a ReadableStream
const src = new EntryStream(db, {
gte: 'b'
})
// Pipe to a stream of choice
const dst = new WritableStream({
write ([key, value]) {
console.log('%s: %s', key, value)
}
})
await src.pipeTo(dst)
Yields:
b: 2
c: 3
To only read keys or values rather than entries:
const { KeyStream, ValueStream } = require('level-web-stream')
await new KeyStream(db).pipeTo(new WritableStream({
write (key) {
console.log(key)
}
}))
Note that WritableStream is a global in browsers. In Node.js it can be imported from stream/web.
Install
With npm do:
npm install level-web-stream
API
stream = new EntryStream(db[, options])
Create a ReadableStream that will yield entries. An entry is an array with key and value properties. The db argument must be an abstract-level database. The optional options object may contain:
highWaterMark(number): the maximum number of entries to buffer internally before ceasing to read further entries. Default 1000.
Any other options are forwarded to db.iterator(options). The stream wraps that iterator. If you prefer to consume entries with for await...of then it's recommended to directly use db.iterator(). In either case, most databases will read from a snapshot (thus unaffected by simultaneous writes) as indicated by db.supports.snapshots.
stream = new KeyStream(db[, options])
Same as EntryStream but yields keys instead of entries, using db.keys() instead of db.iterator(). If only keys are needed, using KeyStream may increase performance because values won't have to be fetched.
stream = new ValueStream(db[, options])
Same as EntryStream but yields values instead of entries, using db.values() instead of db.iterator(). If only values are needed, using ValueStream may increase performance because keys won't have to be fetched.
Contributing
Level/web-stream is an OPEN Open Source Project. This means that:
Individuals making significant and valuable contributions are given commit-access to the project to contribute as they see fit. This project is more like an open wiki than a standard guarded open source project.
See the Contribution Guide for more details.
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