// 不考虑字母

function s2i(s) {

    return s.split('').reduce(function(a, c) {

        var code = c.charCodeAt(0);

        if (48<=code && code < 58) {

            a.push(code-48);

        }

        return a;

    }, []).reduce(function(a, c) {

        return 10*a + c;

    }, 0);

}

function versionCmp(s1, s2) {

    var a = s1.split('.').map(function(s) {

        return s2i(s);

    });

    var b = s2.split('.').map(function(s) {

        return s2i(s);

    });

    var n = a.length < b.length ? a.length : b.length;

    for (var i = 0; i < n; i++) {

        if (a[i] < b[i]) {

            return -1;

        } else if (a[i] > b[i]) {

            return 1;

        }

    }

    if (a.length < b.length) return -1;

    if (a.length > b.length) return 1;

    var last1 = s1.charCodeAt(s1.length-1) | 0x20,

        last2 = s2.charCodeAt(s2.length-1) | 0x20;

    return last1 > last2 ? 1 : last1 < last2 ? -1 : 0;

}

console.log( versionCmp('1.2.3a', '1.2.3b') );

console.log( versionCmp('1.2.13a', '1.2.3b') );

console.log( versionCmp('1.2.12', '1.2.12c') );

console.log( versionCmp('1.3', '1.2.12c') );

console.log( versionCmp('1.2.3a', '1.2.3A') );

console.log('------------------------------');

console.log( versionCmp('1.2.3z', '1.2.4') );