i want to validate the payment form in square payments sdk before submitting, suggest me a event that will give complete card state that is valid or invalid.
The Web Payments SDK does a light validation of the card to check that the card information is a valid card format before allowing you to submit the card. Otherwise you can listen for CardInputEvents. 
thank you so much for your reply bryan… In card input events we are getting status of each input field seperately, is there any way or event to get complete form fields status at once…?
You could listen for isPotentiallyValid or isCompletelyValid events. This will tell you whether the input value is not empty and is being validated and the SDK has validated the input field contents.