String calculator

test312.js

//10+5*2
const str = '10+5*2';

let total = 0;
let currentNum = '';
let operator = '';

for (var i = 0; i < str.length; i++) {
    if (parseInt(str[i]) > -1) {
        currentNum = currentNum + str[i];
    } else {
        if (str[i] !== '') {
            operator = str[i];
        }
        // total = currentNum;
        currentNum = '';
    }

    if (total >= 0 && currentNum > 0 && operator !== '') {
        if (operator === '+') {
            total = parseInt(total) + parseInt(currentNum);
        }
        
        if (operator === '*') {
            total = parseInt(total) * parseInt(currentNum);
        }
        operator = '';
    } else {
        if (currentNum > 0) {
            total = currentNum;
        }
    }
}

console.log('string total', total);