html select 的操作

1：检查是否有选中项

  if(objselect.selectedIndex>-1){//有选中}else{//未选中}

2：动态显示下拉框

var myselect = document.CreateElement_x("select");myselect.id = "myselect";document.body.appendChild(myselect);

3：添加选项

var myselect = document.getElementByIdx("myselect");myselect.add(new Option("文本","值"));//这里需要大写

4：删除所有选项

var myselect = document.getElementByIdx("myselect");myselect.options.length = 0;

5：删除某一个选项

var myselect = document.getElementByIdx("myselect");myselect.options.remove(myselect.selectedIndex);

6：获得选中项的值和文本，修改选项

 var myselect = document.getElementByIdx("myselect");var value = myselect.options(myselect.selectedIndex).value;var text = myselect.options(myselect.selectedIndex).text;myselect.options(myselect.selectedIndex) = new option("文本","值")

7：删除

var myselect = document.getElementByIdx("myselect");myselect.parentNode.removeChile(myselect);

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