Question

I need to evaluate user-entered arithmetic expressions like “2 * (3 + 4)” in Javascript but I don’t want to use eval for security reasons.

I could strip out all the characters that are not numbers or operators but I’m not sure this would be safe anyway and it would be nice if the user could use functions like cos, sqrt, etc…

Are there any Javascript libraries that do arithmetic expression evaluation?

Answer 1

You can try JavaScript Expression Evaluator:

This library is a modified version of
Raphael Graf’s ActionScript Expression
Parser. When I wrote the JavaScript
Function Plotter, I wanted a better
alternative to using JavaScript’s eval
function. There’s no security risk
currently, because you can only run
code in your own browser, but it’s not
as convenient for math (Math.pow(2^x)
instead of 2^x, etc.).

Then your code will be like that:

console.info ( Parser.evaluate( "2 * (3 + 4)" ) ); //prints 14

The source code is on GitHub and it’s published on npm as expr-eval. Can be used like so:

import { Parser } from 'expr-eval';

console.log(Parser.evaluate("2 * (3 + 4)")); // 14