Exclude specific email domains on submission form

I want to exclude certain email domains (gmail, etc.) on a submission form but I am not sure how to do this. Would this be something I can do in the html itself?

If I add the following javascript to my html form code will this work?

<script>
  var label = 'email required';
  var standardEmail = /^(?!.+@(gmail|yahoo|hotmail|comcast|msn)\..+)(.+@.+\..+)$/; 
  var errorMessage = 'field: Please enter your business email address.';
        
window.__custom_form_validations = [
    {
      fieldName: label,
      validationFn: function (input) {
        return {
          isValid: standardEmail.test(input.value),
          message: window._Translate.get(errorMessage),
        };
      },
    },
  ];
</script>

I have tried this and it didn't work. I am unsure of where I need to place this code. Any help would be appreciated.