BatchLoader
BatchLoader is a batching utility for data fetching layer to reduce requests round trips, inspired by Facebook's DataLoader, written in TypeScript.
BatchLoader is a simplified version of Facebook's DataLoader and can be used with any database such as MongoDB or with GraphQL.
Comparison to DataLoader
+ written in TypeScript
+ Further reduces data fetching requests by filtering out duplicate keys
+ Similar api as DataLoader
+ Smaller in size (0 dependencies)
+ MappedBatchLoader can be used to compose a new loader using existing loaders.
- Removed caching functionalities. Leave caching to better cache libraries.
It is a very simple batcher that only does batching, and it does it very well.
Getting Started
First, install BatchLoader using npm.
npm install --save batchloader
or with Yarn,
yarn add batchloader
Note: BatchLoader assumes a JavaScript environment with global ES6
Promise
, available in all supported versions of Node.js.
Batching
Create loaders by providing a batch loading function and key transformation function (used for finding duplicate keys).
; ; ; ; ; // batch function receives only one id1 since duplicate ids. Still returs three items just as requested. ; // batch function receives [id1, id2, id3] only without duplicate ids.
Batch Function
A batch loading function must be of the following type:
Value | Promise<Value> // keys.length === values.length
Constraints
- keys.length === values.length
- keys[i] => values[i]
- keys.length > 0
KeyToUniqueId Function
A function must return string value given a key:
string
If key is not uniquely identifiable, simply pass null
instead. This will disable filtering out duplicate keys, and still work the same way.
;;; // batch function receives [k1, k2, k1] as keys
MappedBatchLoader
You can map a loader to create another loader.
; ; ;// or; // same APIs as BatchLoader;; ;// or;
Caching
Unlike DataLoader, BatchLoader does not do any caching. This is intentional, because you may want to use your favorite cache library that is best suited for your own use case. You can add caching ability easily like so:
; ; delete userCache; // delete cache by keyuserCache = user2; // add cache by keyuserCache =; // empty cache
Choose whatever caching library you like and simply add it like above.