mapboxgl-legend

Add a legend to a mapbox-gl map by parsing layer layout & paint expressions.

Properties currently supported:

• fill-color
• circle-color
• circle-radius
• icon-image

Expressions currently supported:

• match
• interpolate
• step
• literals

Get started

Install npm package

npm install mapboxgl-legend

Add legend control to map

import LegendControl from 'mapboxgl-legend';

const legend = new LegendControl();
map.addControl(legend, 'bottom-left');

Add layers as usual, and the legend will be autogenerated

map.addLayer({
	id: 'density',
	type: 'circle',
	source: 'demographic',
	paint: {
		'circle-radius': [
			'interpolate', ['linear'],
			['to-number', ['get', 'density']],
			100, 10,
			200, 17,
			500, 30,
			1000, 50,
			2000, 75
		],
		'circle-color': [
			'match',
			['get', 'ethnicity'],
			'White', '#f1e8c8',
			'Black', '#443722',
			'Hispanic', '#aa9761',
			'Asian', '#e8e59d',
			/* other */ '#ccc'
		]
	},
});

Options

A few options can be passed on legend initialization.

option	type	default	description
collapsed	Boolean	false	Set legend panels collapsed on load
toggler	Boolean	false	Add button to show and hide layers
layers	Array[regex]	undefined	List of layers to be added. If undefined all layers will be added

There are also a few options that be defined as a per-layer basis using the style metadata object.

option	type	description
name	String	Set the panel title name
unit	String	Add a unit to all labels
labels	Object	Map a value to a text that replaces it as a label

map.addLayer({
	id: 'density',
	type: 'circle',
	source: 'demographic',
	paint: { /* ... */ },
	metadata: {
		name: 'Population Density',
		unit: `k/km²`
	}
});

Styles

Legend defaults to a simple design inspired by standard mapbox-gl controls, but can be tunned by changing CSS variables. Check default values in /src/_variables.scss