RiMath is a small math expression evaluator in JavaScript. It uses the shunting-yard algorithm to convert expressions to Reverse Polish Notation.
This code is battle-tested and has been in use since 2013 at Turnkey Telemetry, both server-side and client-side.
If using Node.js, you can easily install with npm:
npm install rimath
Otherwise, just copy rimath.js into your project. It also works fine
client-side.
var rimath = require('./rimath.js');
//Basic usage
var expr = rimath.compile("100+5*2");
console.log(expr()); //110
//Call external function
var triple = function(s) {s.push(s.pop()*3);};
var funcs = {trip: [1, triple]};
expr = rimath.compile("trip(100)", funcs);
console.log(expr()); //300
//Detect error (unbalanced paran)
expr = rimath.compile("1+(4*2");
console.log(expr); //{text: '1+(4*2', index: 6, token: '', type: 'paren'}