function _sort(arr){
    var len = arr.length;
    for(var i = 1; i < len; i++){
        var j = i - 1;
        while((j >= 0) && (arr[j] > arr[j+1])){
            var a = arr[j];
            arr[j] = arr[j+1];
            arr[j+1] = a;
            j--;
        }
    }
    alert(arr);
}

排序：冒泡