Package Exports

mapboxgl-legend

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Readme

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