Library: seq()

seq() module is a function, which creates a chain of asynchronous functions specified dynamically as an array. Each function will be called with a resolved result of a previous function.

For example, for three functions f, g, h, which return a Promise object, all those examples are identical:

seq(f, g, h)(init).then(result => console.log(result));

seq([f, g, h])(init).then(result => console.log(result));

(async init => {
  const x = await f(init);
  const y = await g(x);
  const z = await h(y);
  return z;
})(init).then(result => console.log(result));

Promise.resolve(init)
  .then(f)
  .then(g)
  .then(h)
  .then(result => console.log(result));

Usage

In a module-enabled environment (like Babel) it can be accessed like that:

import seq from '@researchnow/reno/src/utils/seq';

In global-based environments (like a browser) it is frequently mapped to Reno.utils.seq.

seq(fns) or seq(...fns)

This function has two signatures. It accepts the following arguments:

• fns is an array of functions. Each function takes a single argument and returns a result, possibly a Promise instance. Each function is called one after another waiting for resolving intermediate promises passing previous results to next functions.

It returns a function, which takes a single argument, which is used to start the chain.

Examples

const getParent = seq([
  id => `/item/${id}`,
  heya.io.get,
  data => `/item/${data.parentId}`,
  heya.io.get
]);

getParent(1).then(parent => console.log(parent));
getParent(2).then(parent => console.log(parent));