Not allow a blank character / space in a input form

Check this Fiddle. Relevant code:

 $(function() {
        $('#input1').on('keypress', function(e) {
            if (e.which == 32){
                console.log('Space Detected');
                return false;
            }
        });
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<input type="text" id="input1" />

Use HTML5's extended input types to apply constraint validation, which will prevent submitting the form with invalid emails in modern browsers:

<input type="email" value="" maxlength="30" name="email" class="formfield w0">

In older browsers, you can detect that the input's type is not "email", as it will default to "text" when a value is considered invalid. I'd recommend blocking the submission of the form, rather than preventing default action of the space key, which could be inadvertently circumvented by pasting or via other input methods.

The following code is an example of this, and should be executed after the document is ready:

var frm = document.getElementById('myform');

if (frm.email.type === 'text') {
    frm.onsubmit = function () {
        if (/\s/.test(frm.email.value)) {
            // Tell your user the field is invalid here, e.g.
            frm.email.className = 'invalid';

            // Prevent form submission
            return false;
        }
    }
}

Working demo: http://jsfiddle.net/hgc7C/

Don't forget that this is not a substitute for server-side form validation.