README.md

Filter

Filter expressions are used to target specific data in a layer. This library implements the semantics specified by the Mapbox GL JS spec.

API

featureFilter(filter)

Given a filter expressed as nested arrays, return a new function that evaluates whether a given feature (with a .properties or .tags property) passes its test.

Parameters

parameter	type	description
filter	Array	mapbox gl filter

Returns Function, filter-evaluating function

Usage

var ff = require('feature-filter');

// will match a feature with class of street_limited,
// AND an admin_level less than or equal to 3,
// that's NOT a polygon.
var filter = [
    "all",
    ["==", "class", "street_limited"],
    ["<=", "admin_level", 3],
    ["!=", "$type", "Polygon"]
]

// will match a feature that has a class of
// wetland OR wetland_noveg.
// ["in", "class", "wetland", "wetland_noveg"]

// testFilter will be a function that returns a boolean
var testFilter = ff(filter);

// Layer feature that you're testing. Must have type
// and properties keys.
var feature = {
    type: 2,
    properties: {
       class: "street_limited"
       admin_level: 1
    }
};

// will return a boolean based on whether the feature matched the filter
return testFilter(feature);