问字母数字字符串降序排序

EN

var arr=["2 xxx","20 axxx","38 xxxx","20 bx","8540 xxxxxx"];
arr.sort(function(a,b){
    a=a.split(" ");
    b=b.split(" ");
    var an=parseInt(a[0],10);
    var bn=parseInt(b[0],10);
    return an<bn?1:(an>bn?-1:(a[1]<b[1]?-1:(a[1]>b[1]?1:0)));
});
console.log(arr);

var arr = [
    "2 xxx",
    "20 axxx",
    "38 xxxx",
    "20 bx",
    "8540 xxxxxx"
    ];

arr.sort(function(a, b) {
    var aParts = a.split(" "),
        bParts = b.split(" "),
        aNum = +aParts[0],   // convert numeric parts
        bNum = +bParts[0];   // to actual numbers

    if (aNum > bNum)
        return -1;
    else if (aNum < bNum)
        return 1;
    else
        return aParts[1].localeCompare(bParts[1]);
});