SignaturePad

https://github.com/szimek/signature_pad

Code to make signature work:

<script src="https://cdnjs.cloudflare.com/ajax/libs/signature_pad/4.1.5/signature_pad.js"></script>

<div class="col-sm-8">
    <canvas id="signature-pad" width="400" height="200"></canvas>
    <button id="clear-button">Clear</button>
</div>

<style>
    #signature-pad {
        border: 1px solid #000;
    }
</style>
<script>
    // Initialize Signature Pad
    var canvas = document.getElementById('signature-pad');
    var signaturePad = new SignaturePad(canvas);

    // Clear button event handler
    var clearButton = document.getElementById('clear-button');

    clearButton.addEventListener('click', function () {
        signaturePad.clear();
    });

    function getSignatureData() {
        //var canvas = document.getElementById('signature-pad');
        //var signaturePad = new SignaturePad(canvas);
        if (signaturePad.isEmpty()) {
            return 'error';
        }
        var signatureData = signaturePad.toDataURL();
        return signatureData;
    }
</script>