AngularJS Tax Validator (South Africa)

taxValidator.js

this.validTax = false;
this.taxValidator = function (taxnumber) {
    taxnumber = taxnumber.split("");
​
    var taxMultiplied = 0;
​
    for (let index = 0; index < taxnumber.length; index++) {
        if ((index % 2) == 1) {
            taxMultiplied += taxnumber[index] * 1;
        }
        else {
            if ((taxnumber[index] * 2) > 9) {
                var num = (taxnumber[index] * 2).toString().split("");
                taxMultiplied += (num[0] * 1) + (num[1] * 1);
            }
            else {
                taxMultiplied += taxnumber[index] * 2;
            }
        }
    }
​
    if (taxMultiplied.toString().split("")[1] === "0") {
        this.validTax = true;
    }
    else {
        this.validTax = false;
    }
}
​
this.taxValidator("0000000000");
console.log(this.validTax);