Backspace String Compare

[jzhangnu]

var backspaceCompare = function(S, T) {
    let t1 = '', t2 = '';

    for (let i = 0; i < S.length; i++) {
        let s = S.charAt(i);
        s !== '#' ? t1 += s : t1 = t1.slice(0, t1.length-1);
    }

    for (let i = 0; i < T.length; i++) {
        let t = T.charAt(i);
        t !== '#' ? t2 += t : t2 = t2.slice(0, t2.length-1);
    }

    return t1 === t2;
}



var backspaceCompare = function(S, T) {
    var i = S.length-1, j = T.length-1,
        sk1 = 0, sk2 = 0;

    while (i >= 0 || j >= 0) {
        while (i >= 0) {
            if (S.charAt(i) === '#') {
                sk1++;
                i--;
            }
            else if (sk1 > 0) {
                sk1--;
                i--;
            }
            else break;
        }
        while (j >= 0) {
            if (T.charAt(j) === '#') {
                sk2++;
                j--;
            }
            else if (sk2 > 0) {
                sk2--;
                j--;
            }
            else break
        }

        if(i >=0  && j >= 0 && S.charAt(i) != T.charAt(j)) return false;
        
        if ((i >= 0) ^ (j >= 0)) return false;

        i--; j--;
    }
    
    return true
}