function firstNonWhitespaceIndex(str) {
        for (var i = 0, len = str.length; i < len; i++) {
            var chCode = str.charCodeAt(i);
            if (chCode !== 32 /* Space */ && chCode !== 9 /* Tab */) {
                return i;
            }
        }
        return -1;
    }
Returns first index of the string that is not whitespace.
If string is empty or contains only whitespaces, returns -1