Validate field value by javascript before submitting an item

I want to validate field value of item before submitting using javascript. I know there is a function onBeforeSaveField to achieve this, I think that this function works on server side. I want to validate it on client side using javascript.

Yes onBeforeSaveField is server side.

I think it is best to make a Faq article for this

Thanks for your reply.
Actually I have some dynamic fields, one of these field should have some value. I want to validate it before submitting item.
As you suggest to read FAQ, that was not my requirement.
I can validate only one field on 'BLUR' event.

Hello

there is a misunderstanding
- i have not asked you to read the FAQ artcile

i said that i want to write a new article
i have not written it yet
(it does not exist yet !)

please answer this question:
is the field that you want to custom validate is a "text/number/custom validation" field ??

(then if it is of the above type, you can add your custom validation via a parameter)

Field types are text and select.

How can I validate it via parameter..??

Hello

yes in text field you can enable "custom" validation

and then configure the custom validation via parameter
also an input "mask" will be shon to the user