Is empty

[gerabu]

How to know if the signature pad is empty?

[Binternet]

Try
console.log( $('#signature').jSignature("getData",'native').length > 0 );

Should return true if its signed.

[gerabu]

It is never truly empty because a guideline is always drawn

[Binternet]

Check the demo:
https://willowsystems.github.io/jSignature/#/demo/

Run the command see it returns false
Then draw and signature and run it again.

[KeithETruesdell]

I had the same issues, and it never returned false when there was a signature line.
This 'issue' had been resolved from the original repo from brinley a couple years ago. This repo is about 6 years old. By changing over to the brinley repo and then doing something like....

if ((typeof jsSigData != 'undefined') && $("##js-signature").jSignature("isModified")) {
     jsSigDataValid = true;
}

you will make sure that there someone singed things.
This also works with the signature line, and in the situation that there is a clear button. If someone signs, then clears, it will return "false" as in nothing is modified. The method above will return true, regardless.

So go with the brinley one.