@thi.ng/transducers-async/intercept.js

Async versions of various highly composable transducers, reducers and iterators

import { compR } from "./compr.js";
import { iterator1 } from "./iterator.js";
function intercept(interceptors = [], src) {
  if (src) return iterator1(intercept(interceptors), src);
  const xform = (rfn) => compR(rfn, async (acc, x) => {
    for (let fn of interceptors) {
      const res = await fn(x);
      if (res == null) return acc;
      x = res;
    }
    return rfn[2](acc, x);
  });
  xform.prepend = (fn) => {
    interceptors.unshift(fn);
  };
  xform.append = (fn) => {
    interceptors.push(fn);
  };
  xform.remove = (fn) => {
    const idx = interceptors.indexOf(fn);
    if (idx >= 0) {
      interceptors.splice(idx, 1);
      return true;
    }
    return false;
  };
  return xform;
}
export {
  intercept
};