@mapbox/expression-jamsession

@mapbox/expression-jamsession

Write Mapbox GL expressions in a more familiar, handwritable, spreadsheet-like, programming-like syntax. This library translates these handwritten formulas into valid spec-compliant Mapbox GL expressions that you can use in a Mapbox style.

Features

• Arithmetic operators (+ - * /) and parentheses work like in high school math, e.g. ((3 + 4) * 2) / 7.
• Expressions are represented like function invocations in programming, e.g. get("population"), log2(get("population")).
• & operator concatenates strings, as in spreadsheet programs.

// Input
2 + 2

// Output
["+", 2, 2]

// Input
max(3, log2(6))

// Output
["max", 3, ["log2", 6]]

// Input
((3 + get("num")) * 2) / 7

// Output
["/", ["*", ["+", 3, get("num")], 2], 7]

// Input
"name: " & get("name")

// Output
["concat", ["name ", ["get", "name"]]]

Caveats

• You can use this library to create expressions that are syntactically acceptable but invalid as Mapbox GL expressions, e.g. notARealExpression(true) outputs ["notARealExpression", true].

Usage

Pass in a string formula and get an expression.

import createExpression from '@mapbox/expression-jamsession';

createExpression('3 + 4'); // ["+", 3, 4]

Changelog

0.1.0

• Initial release.