Flatbush

A really fast static spatial index for 2D points and rectangles in JavaScript.

An efficient implementation of the packed Hilbert R-tree algorithm. Enables fast spatial queries on a very large number of objects (e.g. millions), which is very useful in maps, data visualizations and computational geometry algorithms. Similar to RBush, with the following key differences:

Static: you can't add/remove items after initial indexing.
Faster indexing and search, with much lower memory footprint.
Index is stored as a single array buffer (to transfer between threads or save as a compact binary file).

Supports geographic locations with the geoflatbush extension. See also: KDBush, a similar library for points.

Usage

js
// initialize Flatbush for 1000 items
const index = new Flatbush(1000);

// fill it with 1000 rectangles
for (const p of items) {
    index.add(p.minX, p.minY, p.maxX, p.maxY);
}

// perform the indexing
index.finish();

// make a bounding box query
const found = index.search(minX, minY, maxX, maxY).map((i) => items[i]);

// make a k-nearest-neighbors query
const neighborIds = index.neighbors(x, y, 5);

// instantly transfer the index from a worker to the main thread
postMessage(index.data, [index.data]);

// reconstruct the index from a raw array buffer
const index = Flatbush.from(e.data);

Install

Install with NPM: npm install flatbush, then import as a module:

js
import Flatbush from 'flatbush';

Or use as a module directly in the browser with jsDelivr:

html
<script type="module">
    import Flatbush from 'https://cdn.jsdelivr.net/npm/flatbush/+esm';
</script>

Alternatively, there's a browser bundle with a Flatbush global variable:

html
<script src="https://cdn.jsdelivr.net/npm/flatbush"></script>

API

`new Flatbush(numItems[, nodeSize, ArrayType, ArrayBufferType])`

Creates a Flatbush index that will hold a given number of items (numItems). Additionally accepts:

nodeSize: size of the tree node (16 by default); experiment with different values for best performance (increasing this value makes indexing faster and queries slower, and vise versa).
ArrayType: the array type used for coordinates storage (Float64Array by default);
other types may be faster in certain cases (e.g. Int32Array when your data is integer).
ArrayBufferType: the array buffer type used to store data (ArrayBuffer by default);
you may prefer SharedArrayBuffer if you want to share the index between threads (multiple Worker, SharedWorker or ServiceWorker).

`index.add(minX, minY[, maxX, maxY])`

Adds a given rectangle to the index. Returns a zero-based, incremental number that represents the newly added rectangle.
If not provided, maxX and maxY default to minX and minY (essentially adding a point).

`index.finish()`

Performs indexing of the added rectangles.
Their number must match the one provided when creating a Flatbush object.

`index.search(minX, minY, maxX, maxY[, filterFn])`

Returns an array of indices of items intersecting or touching a given bounding box. Item indices refer to the value returned by index.add().

js
const ids = index.search(10, 10, 20, 20);

If given a filterFn, calls it on every found item (passing the item's index & bounding box coordinates)
and only includes it if the function returned a truthy value.

js
const ids = index.search(10, 10, 20, 20, (i) => items[i].foo === 'bar');

Alternatively, instead of using the array of indices returned by search, you can handle the results in the function:

js
index.search(10, 10, 20, 20, (i, x0, y0, x1, y1) => {
    console.log(`Item found: ${items[i]}, bbox: ${x0} ${y0} ${x1} ${y1}`);
})

`index.neighbors(x, y[, maxResults, maxDistance, filterFn])`

Returns an array of item indices in order of distance from the given x, y
(known as K nearest neighbors, or KNN). Item indices refer to the value returned by index.add().

js
const ids = index.neighbors(10, 10, 5); // returns 5 ids

maxResults and maxDistance are Infinity by default.

If given a filterFn, calls it on items that potentially belong to the results (passing the item's index)
and only includes an item if the function returned a truthy value.
Unlike search, it shouldn't be used for handling results.

`Flatbush.from(data[, byteOffset])`

Recreates a Flatbush index from raw ArrayBuffer or SharedArrayBuffer data
(that's exposed as index.data on a previously indexed Flatbush instance).
Very useful for transferring or sharing indices between threads or storing them in a file.

Properties

data: array buffer that holds the index.
minX, minY, maxX, maxY: bounding box of the data.
numItems: number of stored items.
nodeSize: number of items in a node tree.
ArrayType: array type used for internal coordinates storage.
IndexArrayType: array type used for internal item indices storage.

Performance

Running node bench.js on a MacBook Pro (M1 Pro, Node v24):

bench	flatbush
index 1,000,000 rectangles	109ms
100 searches 10% area	64ms
1000 searches 1% area	66ms
10000 searches 0.1% area	150ms
10000 searches 0.01% area	51ms
10000 searches 0.001% area	31ms
10000 searches of 1 neighbor	30ms
10000 searches of 100 neighbors	127ms
1 search of 1,000,000 neighbors	84ms