README.md

Math expression parser and evaluator

Fast and small (less than 2KB minified and gzipped) zero-dependency math expression parser and evaluator.

import evaluate from '@emmetio/math-expression';

console.log(evaluate('2 * (-3 + 5)')); // 4

Motivation

In JavaScript, you can use built-in eval() function to evaluate expressions:

console.log(eval('2 * (-3 + 5)')); // 4

But in most modern JavaScript environments eval() function is considered harmful since it can evaluate any arbitrary JS code. And in some cases (like in Atom editor) it’s disabled by default due to security reasons.

With @emmetio/math-expression module you can safely parse & evaluate basic math expressions in any JS environment.

Extract expression from text

This module is used by Emmet project to evaluate math expression in-place in code source. A default user workflow is to enter math expression somewhere in source code and run action to evaluate it. You can use extract function to extract math expression from given source code, starting at specified position:

import evaluate, { extract } from '@emmetio/math-expression';

const code = 'Here goes math: 2 + 3 foo bar';
const [start, end] = extract(code, 21); // 16, 21
const expr = code.substring(start, end); // 2 + 3
console.log(evaluate(expr)); // 5