巧用sel.options[sel.selectedIndex].text与try{}catch{e}{}操作SELECT选项值
当select.value=value被赋予一个不存在的值时如果在这个时候用sel.options.text来获取当前选择文本会抛出异常。本文主要思想就是catch抛出的异常来断定select中不存在此value的选项，感觉这样做比循环获取每个option的value与新的value值比对是否相等更有效率，废话不多说，上菜！<html><head><title>JS</title><script type="text/javascript">function $(id){return document.getElementById(id);}String.prototype.trim=function(){return this.replace(/(^\s*)|(\s*$)/g,"");}function init(){var originalSel = $("originalSel");originalSel.options=new Option("text1","1");originalSel.options=new Option("text2","2");originalSel.options=new Option("text3","3");originalSel.options=new Option("text4","4");originalSel.options=new Option("text5","5");}function alertText(){var value = prompt('请您输入value值','');if(value==null||value.trim()==""){return;}var originalSel = $("originalSel");originalSel.value=value;try{var text = originalSel.options.text;alert("value="+value+"对应的text是"+text);}catch(e){if(originalSel.options){originalSel.options.selected=true;}alert("您输入的value不存在！");}}function add(){var textValue = prompt("请你输入Text,Value","text,value");if(textValue==null){alert("请您输入text,value!");return;}var ary = textValue.split(",");if(ary.length<2||ary.trim()==""||ary.trim()==""){alert("key,value值不能为空！");return;}var text = ary;var value = ary;var selObj = $("originalSel");selObj.value=value;try{selObj.options.text;alert("select中已存在value为"+value+"的选项！");return;}catch(e){selObj.options=new Option(text,value);selObj.value=value;alert("增加成功！");}}function remove(){var value = prompt('请您输入value值','');if(value==null||value.trim()==""){return;}var originalSel = $("originalSel");originalSel.value=value;try{originalSel.options.text;originalSel.remove(originalSel.selectedIndex);alert("删除成功！");}catch(e){if(originalSel.options){originalSel.options.selected=true;}alert("select中不存在value="+value+"的选项！");}}</script></head><body ><select id="originalSel" style="width:150px"></select><br><input type="button"value="alertText"><input type="button"value="addOption"><input type="button"value="removeOption"></body></html>
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