How do I restrict text to 100 characters of a custom field via the JIRA API?

[SRIDHAR]

Please post the sample code for better understandings. I am pretty new to plugin development and jira.

[Nic Brough -Adaptavist-]

Depends - are you using an existing field? Are you writing your own field? Do you want to do it in html, or just validate the length after the user posts something? Or drop the extra characters?

As an aside, you probably won't get sample code here. We prefer you to understand what you're doing than parrot code that someone else has made the effort to learn/write etc.

[SRIDHAR]

I am using an existing field that is out of the box. I want to restrict to 100 characters only to a specific project . I want to do it in a simple way so that it is easy to apply in different environments. This needs to be done before posting . I have tried javascript but it didn't work. This what I tried in Javascript

<script type="text/javascript">
customLimitField = document.getElementById("customFieldId_10900");
customLimitField.onKeypress = limitText;
function limitText(){
customLimitField = document.getElementById("customFieldId_10900");
if(customLimitField.text.length >= 50)
{
customLimitField.value = customLimitField.value.substring(0,50);
}
}
</script>

Please help me to understand this and fix it.

[SRIDHAR]

Javascript is not a perfect solution. I wrote my own custom field and restricted to 100 characters using the API and sample code from google.