Create a transform stream from an async iterator
npm install @sounisi5011/stream-transform-from
!Supported Node.js version: ^12.17.x || 14.x || 15.x || 16.x || 17.x || >=18.x
[stream.Transform class]: https://nodejs.org/docs/latest/api/stream.html#stream_class_stream_transform
[Buffer object]: https://nodejs.org/api/buffer.html
Create a [transform stream][stream.Transform class] from an async iterator.
This is the last piece needed to convert between streams and async iterators/generators.
* No dependencies
This package uses only the Node.js built-in [stream.Transform class].
* Strict type definition
The exact type definitions for arguments and return values will be generated based on the objectMode option.
* Encoding arguments can be used
You can use encoding, which is passed as the second argument of the transform._transform() method.
This allows you to safely convert a string to [Buffer object].
``sh`
npm install @sounisi5011/stream-transform-from
`sh`
yarn add @sounisi5011/stream-transform-from
`sh`
pnpm add @sounisi5011/stream-transform-from
`js
const fs = require('fs');
const stream = require('stream');
const { transformFrom } = require('@sounisi5011/stream-transform-from');
stream.pipeline(
fs.createReadStream('input.txt', 'utf8'),
transformFrom(async function*(source) {
for await (const { chunk } of source) {
yield chunk.toString('utf8').toUpperCase();
}
}),
fs.createWriteStream('output.txt'),
error => {
if (error) {
console.error(error);
} else {
console.log('done!');
}
}
);
`
`js
const stream = require('stream');
const { transformFrom } = require('@sounisi5011/stream-transform-from');
stream.pipeline(
stream.Readable.from([1, 2, 3]),
transformFrom(
async function*(source) {
for await (const { chunk } of source) {
yield chunk + 2;
}
},
{ objectMode: true }
),
// ...
error => {
if (error) {
console.error(error);
} else {
console.log('done!');
}
}
);
`
`js
const stream = require('stream');
const { transformFrom } = require('@sounisi5011/stream-transform-from');
stream.pipeline(
// ...
transformFrom(
async function*(source) {
for await (const { chunk, encoding } of source) {
if (typeof chunk === 'string') {
yield Buffer.from(chunk, encoding);
}
}
},
{ writableObjectMode: true }
),
// ...
error => {
if (error) {
console.error(error);
} else {
console.log('done!');
}
}
);
`
`js
const { transformFrom } = require('@sounisi5011/stream-transform-from');
// The return value is a Transform stream.
const transformStream = transformFrom(
async function*(source) {
// source is AsyncIterableIterator<{ chunk: Buffer, encoding: BufferEncoding }>
// or type
// The value returned by yield keyword will be passed as the first argument of transform.push() method.
},
// The second argument is an options for the Transform stream.
// The options are passed to the constructor function of the Transform class.
// However, the following fields are not allowed:
// + construct
// +
// +
// +
// +
// +
// +
// +
// The fields listed above will be ignored if specified.
{}
);