<script>
window.module.lp.form.data.validationRules['field_name'].digits = true;
</script>
Replace 'field_name' with the ID of your form field you want to add this validation to.
<script>
window.module.lp.form.data.validationRules['field_name'].digits = true;
</script>
Replace 'field_name' with the ID of your form field you want to add this validation to.