promise-mate

Promise.all fulfillment for many Promises to many callbacks to prevent duplicate calls when there are shared requirements.

Use cases

Use promise-mate if you have multiple Promises to run synchronously that are required by multiple callbacks, some of which have overlapping requirements. This is particularly useful for modular callbacks that may not always be called as well as for resource fetching.

Installation

npm i promise-mate

Or,

yarn add promise-mate

Example

The below example fetches data to update the webpage.

import Mate from 'promise-mate'

const runner = new Mate({
  users() {
    return fetch('/api/users').then(res => res.json()).then(json => json.users)
  },
  purchases() {
    return fetch('/api/purchases').then(res => res.json()).then(json => json.purchases)
  },
  products() {
    return fetch('/api/products').then(res => res.json()).then(json => json.products)
  },
  calendar() {  // Note: this Promise definition is not requested below so will not be run
    return fetch('/api/calendar').then(res => res.json()).then(json => json.calendar)
  }
});

runner
  .all([
    {
      requires: 'users',
      then(users) {
        // Update the user list!
      }
    },
    {
      requires: ['products', 'purchases'],
      then(products, purchases) {
        // Update product list to show if something's been bought
      }
    },
    {
      requires: [{ uuid: 1265723 }, 'users', 'products', 'purchases'],
      then(userData, users, products, purchases) {
        // Show user's latest purchases
      }
    }
  ])
  .then(() => { console.log('Page updated!') })
  .catch(() => { console.error('Error updating page') })

API

Mate.all

Run all actions.

Mate.all(definitions, actions)

Arguments

• definitions - Key-indexed object with values that are functions that return Promises (or something else).
• actions - Array of objects defining requirements and callbacks.
  • actions[i].requires - Requirements to be passed as arguments to the callback. Can be a singular requirement or an array of requirements. Singular requirements cannot be an array. If a requirement is not a key in definitions, will resolve the requirement.
  • actions[i].then - Function to call when requirements resolve. Passes results as arguments in order of actions[i].requires.

Returns

• Promise<any[]> - An array of what each action's callback returns.

new Mate

Create a Mate with stored definitions.

var runner = new Mate(definitions)

Arguments

• definitions (optional) - Key-indexed object with values that are functions that return Promises (or something else).

Mate.prototype.define

Store a Promise generating function.

runner.define(key, definition)

Arguments

• key - Key for definition.
• definition - Function that returns a Promise (or something else since Promise.all will just resolve non-promises).

Returns

• The Mate instance.

Mate.prototype.undefine

Delete a definition

runner.undefine(key)

Arguments

• key - Key for deletion.

Returns

• The Mate instance.

Mate.prototype.all

Run all actions.

runner.all(actions)

Arguments

• actions - Array of objects defining requirements and callbacks.
  • actions[i].requires - Requirements to be passed as arguments to the callback. Can be a singular requirement or an array of requirements. Singular requirements cannot be an array. If a requirement is not a key in definitions, will resolve the requirement.
  • actions[i].then - Function to call when requirements resolve. Passes results as arguments in order of actions[i].requires.

Returns

• Promise<any[]> - An array of what each action's callback returns.