asStream

asStream() creates a Duplex stream from any function. It supports regular functions, asynchronous functions, generator functions, and asynchronous generator functions. The result can be used as a regular stream.

In most cases you don't need to use it directly. It is used internally by chain().

The example of usage:

import asStream from 'stream-chain/asStream.js';
// const {asStream} = require('stream-chain/asStream.js');

asStream(fn[, options])

The function accepts the following arguments:

• fn — any function, generator function, or asynchronous function.
• options — an optional object used as an argument for the Duplex constructor.
  • See Duplex for more details.
  • If not specified readableObjectMode and writableObjectMode are set to true.

The function returns a Duplex stream, which wraps the fn.

fn can use any special values defined in defs (and re-exported in chain()):

• none, null, undefined — no value is produced. Node.js streams reserve null/undefined for end-of-stream signaling, so they are treated as none.
• stop, Stop — terminates the stream.
• many() — multiple (or none) values are produced.
• finalValue() — its payload is treated as a regular value.
  • Native streams do not support this feature.

Note: This differs from gen() and fun(), which are general-purpose compositors and pass null/undefined through the pipeline like any other value.

Examples

import asStream from 'stream-chain/asStream.js';

const stream = asStream(x => x * x);

dataSource.pipe(stream);
// if dataSource produces: 1, 2, 3
// then the result will be: 1, 4, 9

See also

• asWebStream() — the Web Streams counterpart. Same dual-role API (pass a Web Streams object → returned as-is; pass a function → returns a duplex pair).
• highWaterMark — backpressure tuning.