Error in console while validating gstin in Polymer JS

I have a Polymer JS code which validates GST Identification number:

<dom-module id="gst">
    <template>
            <div>
                <label for="gstid" class="gstlabel">GSTIN</label>
                <input type="text" id="gstid" name="gstid" on-submit="gstid_validation(gstid)">
            </div>
    </template>

    <script>
        Polymer({
            is: 'gst',
            gstid_validation: function(gstin) {
                var gstin_count = length(gstin);
                var pattern = "qr/\d{2}[A-Z]{5}\d{4}[A-Z][A-Z\d]Z[A-Z\d]/";
                if (gstin_count !== 15 && gstin !~ pattern) {
                    return 'Invalid GSTIN';
                }
            }.
        });
    </script>
</dom-module>

I get the following error in console:

Uncaught SyntaxError: Unexpected token !

Can anyone please help?

Thanks in advance

Solution

As I wrote in the comment also, that is clearly a problem with the second part of your if statement, gstin !~ pattern.

Assuming that what you want is to match a regex the correct syntax would be something like:

if (gstin_count !== 15 && pattern.text(gstin))

Please note that there are several other issues with your code. Just to name a few:

Your pattern variable holds a string, not a regex. For a regex you wouldn't use the quotations as delimiters. Also modifiers go at the end of regexes.
In JS there's no length function, so if you don't have it customly implemented most likely you want gstin.length
custom elements need to have dashes in their name (gstin-validator, gst-in, etc),
when you define an event handler you need to pass the method name, not to call it, like I told you in this other post: Error in console while hiding the link on click through Polymer/Dom