Checking the signature with Javascript

To check if the signature has been signed from within the form itself, first get the field using

var digSig = event.target.getField("form1[0].#subform[0].Submit[0].Signature[0]");

Its important to use the fully qualified path to the signature.

Once thats done you can use this check the status

var status = digSig.signatureInfo().status;

The possible values you can get are

-1: not a signature field
0: signature is blank
1: unknown status
2: signature is invalid
3: signature is valid, identity of signer could not be verified
4: signature and identity of signer are both valid