怎样用js动态创建select下拉菜单？

1、
function test()
{
    var i=0;j=0;
    for(i=0;i<64;i++)
    {
        document.write('<select>')
        for (j=0;j<4;j++)
        {
            if(j==0)
                document.write('<option value='+j+'>'+'aa'+'<\/option>')
            else if(j==1)
                document.write('<option value='+j+'>'+'bb'+'<\/option>')
            else if(j==2)
                document.write('<option value='+j+'>'+'cc'+'<\/option>')
            else if(j==3)
                document.write('<option value='+j+'>'+'dd'+'<\/option>')
        }
        document.write('<\/select>')
    }
}

window.onload = function()
{    for( var i=0;i<64;i++)
    {
        document.write('<select>')
        for ( var j=0;j<4;j++)
        {
           document.write('<option value='+j+'>'+j+'<\/option>')
        }
        document.write('<\/select>')
    }
}