compile-filter

This library is forked from mapbox/feature-filter, but adapted to work with any object. This library implements the semantics specified by the Mapbox GL JS spec, but supports arrays as keys as well as strings, in order to filter against nested properties

API

compile(filter)

Given a filter expressed as nested arrays, return a new function that evaluates whether a given feature passes its test.

Parameters

| parameter | type | description | | --------- | ----- | ---------------- | | filter | Array | mapbox gl filter |

Returns Function, filter-evaluating function

Usage

var compile = require('compile-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]
]

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

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

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

Filter expression language

Existential Filters

["has", key] object[key] exists

["!has", key] object[key] does not exist

Comparison Filters

["==", key, value] equality: object[key] = value

["!=", key, value] inequality: object[key] ≠ value

[">", key, value] greater than: object[key] > value

[">=", key, value] greater than or equal: object[key] ≥ value

["<", key, value] less than: object[key] < value

["<=", key, value] less than or equal: object[key] ≤ value

Set Membership Filters

["in", key, v0, ..., vn] set inclusion: object[key] ∈ {v0, ..., vn}

["!in", key, v0, ..., vn] set exclusion: object[key] ∉ {v0, ..., vn}

Combining Filters

["all", f0, ..., fn] logical AND: f0 ∧ ... ∧ fn

["any", f0, ..., fn] logical OR: f0 ∨ ... ∨ fn

["none", f0, ..., fn] logical NOR: ¬f0 ∧ ... ∧ ¬fn

A value (and v0, ..., vn for set operators) must be a string, number, or boolean to compare the property value against.

Set membership filters are a compact and efficient way to test whether a field matches any of multiple values.

The comparison and set membership filters implement strictly-typed comparisons; for example, all of the following evaluate to false: 0 < "1", 2 == "2", "true" in [true, false].

The "all", "any", and "none" filter operators are used to create compound filters. The values f0, ..., fn must be filter expressions themselves.

["==", "class", "street_major"]

This filter requires that the class property of each feature is equal to either "street_major", "street_minor", or "street_limited".

["in", "class", "street_major", "street_minor", "street_limited"]

The combining filter "all" takes the three other filters that follow it and requires all of them to be true for a feature to be included: a feature must have a class equal to "street_limited", its admin_level must be greater than or equal to 3.

[
  "all",
  ["==", "class", "street_limited"],
  [">=", "admin_level", 3]
]