javascript 比较版本号大小 字符串

* 不用系统比较大小的函数

// 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;
}

test:

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') );