Data input form validation by using Javascript

We can validate the entry of any form by using JavaScript. This is a client side JavaScript form validation and you can check server side php form validation also. Before taking up any client side validation it is advisable to check JavaScript is not disabled in the client browser.
Demo of Simple Text input validation
Notice how you are prevented from submitting form unless the text input field is filled.

Some of the requirement of validation before allowing form to be submitted is here. These validations are some sample only and actual requirement may change.

Text Box:

Can't be left blank, only text or only numeric data to be entered. There can be an upper limit of data entered in a textbox.

Radio button ( Period button ) :

One of the several radio button to be selected before submitting the form

Checkbox :

User must check before submitting. One or more to be checked.

Listbox ( dropdown box ) :

One of the options has to be selected before submitting.

Email validation :

Check email address as entered by user.

Disable radio button :

Enable or disable period button by using a checkbox.

datalist:

Adding options to a datalist.

TextArea :

Can't be left blank or some minimu data to be entered. There can be a restriction on maximum number of text to be entered.

Element / Functions	Description
Submit Button	Enable or Disable submit button of a web form
Reset Button	Resetting button on a form and Resetting the form by getElementById
getElementById	Managing elements of a form by using getElementById

JavaScript Basic

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Javascript Form Validation