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When a select box requires on the fly validation, HTML and JavaScript doesn’t quite support any way of reverting to a previous choice if the validation fails. You cant trigger an onchange event without first updating the select box to a different value. On the other hand, onclick occurs before the choice is made.
If you set a “selected” tag within an option tag on page load, you can easily revert to a previous value by resetting the form or running reset() on the form. However this kinda makes the selected value pretty static.
...
The following example will firstly show the javascript code
Code:
<script type="text/javascript"> | |
| |
var selectList_cache; // Variable for remember previous choice | |
| |
function validateList(val) | |
{ | |
if(isValid()) | |
{ | |
alert("Validated successfully!"); | |
} | |
else | |
{ | |
alert("Failed the validation so reverting"); | |
document.getElementById("selectList").value=selectList_cache; | |
} | |
} | |
</script> |
Followed by the HTML select box,
Code:
<select name="selectList" id="selectList" onclick="selectList_cache=this.value" onchange="validateList(this.value);return false"> | |
<option value="1">1</option> | |
<option value="2">2</option> | |
<option value="3">3</option> | |
<option value="4">4</option> | |
</select> |
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3 comments
awesome,
very Good tip 
You might want to use the "onfocus" event for setting the cache value. Onclick doesn't work when using a keyboard. 
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Brinley Ang is a sysadmin, web dev, coder, geek boy, jedi knight fragger, caffine addict, deaf meloncholic and rockstar wannabe. Listens to the sex pistols and a wide assortment of heavy metal.
