API · Core

extend()

Install a custom method on the shared Exstream prototype.

Signature

extend(name: string, fn: (this: Exstream<any, any>, ...args: any[]) => unknown): void

Example

exstream.extend('double', function () {
  return this.map((value) => value * 2)
})

exstream([1, 2]).double().valuesSync()

Behavior

The assignment is global to the loaded module instance and affects existing and future streams. Pipelines dynamically proxy methods found on Exstream.prototype, so a custom method can be recorded there too when it returns an Exstream-compatible operator chain.

There is no collision protection, name validation, uninstall API, or automatic TypeScript declaration augmentation. Reusing a built-in name replaces it. Use a unique name, a normal function when this is required, and module augmentation for typed consumers.

extend() performs no wrapping around the custom implementation; validation, errors, contexts, pressure, and cancellation are the extension author’s responsibility. Prefer reusable pipeline() or through(fn) when global prototype mutation is unnecessary.

Related

pipeline(), through(), consume()