developit

/** Async version of Array.prototype.reduce()
 *  await reduce(['/foo', '/bar', '/baz'], async (acc, v) => {
 *    acc[v] = await (await fetch(v)).json();
 *    return acc;
 *  }, {});
 */
export async function reduce(arr, fn, val, pure) {
  for (let i=0; i<arr.length; i++) {
    let v = await fn(val, arr[i], i, arr);
    if (pure!==false) val = v;