Is there any way to do array operations by order in javascript?

<pre> function getResult(exp) {
            exp = '1 * ' + exp;
            var parts = exp.split(' ');
            var result, num = [], exp = []; var formu = [];

            for (var i = 0; i < parts.length; i++) {
                var item = parts[i].trim();
                if (isNaN(item))
                    exp.push(item);
                else
                    num.push(item);
            }
            for (var i = 0; i < num.length + 1; i++) {
                var expr = exp[i - 1] == undefined ? '' : exp[i - 1];
                var numr = num[i] == undefined ? '' : num[i];
                var str = expr + numr;
                if (i == 0)
                    str = '1'
                result = result == undefined ? '' : result;
                result = eval(result + str);
            }
            return result;
        }

        console.log(getResult(  "10 * 20 / 30 - 60 + 2"))  //- 51.3333