TaskBatcher

TaskBatcher is a utility that lets you easily run multiple tasks in a single batch. Partially inspired by Facebook's DataLoader

Getting Started

Install with npm

npm i --save taskbatcher

TaskBatcher uses the global Promise class, so use a polyfill or transpile with babel or tell everyone who uses your website to get a decent browser.

You'll need to provide a runTasksFn function when creating a new TaskBatcher.

import TaskBatcher from 'taskbatcher';
const taskBatcher = new TaskBatcher(keys => runTasks(keys))

The runTasksFn function takes on argument, [key], and should return a Promise that either resolves with [value | Error] or { [key]: value | Error, [key2]: value2 | Error }.

Then add tasks to the batcher using addTask. TaskBatcher will add your keys to a queue, and will run your runTasksFn function after a delay (default 50ms) since the last time the function was called (aka, it debounces). They delay's won't stack indefinitely, however, and will eventually run after the maxWait ( default 250ms) limit is reached.

taskBatcher.addTask(1).then(data => console.log(`Data received! ${data}`));

API Request Example

TaskBatcher was initially designed around making requests, but it ended up being generic enough to handle any sort of task. Here's how to use it to make api requests:

const getUsersByIds = async (ids) => fetch(`/users?id=${ids.join(',')}`).then(resp => resp.json());

const userFetcher = new TaskBatcher(getUsersByIds);
userFetcher.addTask(1).then(user => console.log(`Here's your user: ${user}`));
userFetcher.addTask(2).then(user => console.log(`Here's another user: ${user}`));
userFetcher.addTask(3).then(user => console.log(`And another user: ${user}`));

In the above example, only one request will be made (fetch('/users?id=1,2,3')).

In case you think it's weird to call addTask on userFetcher, feel free to rename the addTask function using the renameAddTaskTo option like so:

const userFetcher = new TaskBatcher(getUsersByIds, { renameAddTaskTo: 'fetch' });
userFetcher.fetch(1).then(user => console.log(`Here's your user: ${user}`));

Note Flow doesn't currently support indexable signature for class declarations, so if you're using flow, you should probably just not do this.

API

class TaskBatcher

new TaskBatcher(runTasksFn, [, options])

Create a new TaskBatcher given a task running function and options.

• runTasksFn: A function which accepts an Array of keys, and returns a Promise which resolves to either an Array of values or a single object with key/value pairs.

• options: An optional object of options:

  • delay: The number of milliseconds to delay
  • maxWait: The maximum time runTasksFn is allowed to be delayed before it’s invoked
  • renameAddTaskTo: Renames the addTask function to the given value

addTask(key)

Adds a key, returning a Promise for the value represented by that key.

• key: A key value to identify your task with.