javascript中为一个下拉框赋初值（打开网页直接显示在下拉框）？

[xingtai]

javascript中为一个下拉框赋初值（打开网页直接显示在下拉框）用window_onload()
请问如何编写

[zl13]

eval("document.frmAnnounce.city.options[i] = " + "new Option" + barray[i]);
eval("document.frmAnnounce.city.options[i].value =" + bnarray[i]);