Parse math strings and solve

equation.js

var equation = "1+(3+(3-2))*5/2";

var process = function(arr) {
	if (arr.length == 1) {
		return parseFloat(arr[0]);
	}

	var number = arr[0];
	var operator = arr[1];
	var slice = 2;

	if (number == "(") {
		var count = 1;
		for (var i = 1; i < arr.length; i++) {
			if (arr[i] == ")") count--;
			if (arr[i] == "(") count++;
			if (count == 0) break;
		}
		number = process(arr.slice(1, i));

		if (i + 1 == arr.length) {
			return number;
		} else {
			operator = arr[i+1];
			arr.splice(0, i+2);
			slice = 0;
		}
	} 

	if (operator == '*' || operator == "/") {
		if (arr[slice+1] == '+' || arr[slice+1] == '-') {
			if (operator == '*') {
				number = number * arr[slice];
			} else {
				number = number / arr[slice];
			}
			operator = arr[slice+1];
			arr.splice(0, 2);
		} else {
			if (operator == '*') return parseFloat(number) * process(arr.slice(slice));
			else return parseFloat(number) / process(arr.slice(slice));
		}
	} 

	if (operator == '-') {
		return parseFloat(number) - process(arr.slice(slice));
	} else if (operator == '+') {
		return parseFloat(number) + process(arr.slice(slice));
	}
};

console.log(process(equation.split('')));