Validation with straight jQuery.

validator.coffee

@@ -0,0 +1,50 @@
+valid_email_local_part = (lpart) ->
+    if lpart is undefined || lpart.length == 0 || lpart.length >64
+        return false
+    # Localpart is one or more atext pieces separated by .s
+    return lpart.match(/^[a-zA-Z0-9!#\$\%&'*+\-/=?^_`{|}~]+(?:\.[a-zA-Z0-9!#\$\%&'*+\-/=?^_`{|}~]+)*$/)
+
+valid_domain_label = (label) ->
+    if label is undefined || label.length > 63 || label.length == 0
+        return false
+    return label.match(/^[a-zA-Z0-9](?:[-a-zA-Z0-9]*[a-zA-Z0-9])?$/)
+
+valid_email_domain = (domain) ->
+    if domain is undefined || domain.length > 255 || domain.length == 0
+        return false
+    # a domain is one or more domain labels separated by .s
+    labels = domain.split(/\./)
+    return ($.grep( labels, (l)->return !valid_domain_label(l) )).length == 0
+
+valid_email = (email) ->
+    parts = email.split('@')
+    return false if !valid_email_local_part(parts[0])
+    return valid_email_domain(parts[1])
+
+display_error_unless = (condition, index) ->
+    select = '.errors li:eq(' + index + ')'
+    if(condition)
+        $(select).hide()
+    else
+        $(select).show()
+
+
+$(() ->
+  $('.errors li').hide()
+  $('input[type="text"]').blur((evt) ->
+      email = evt.target.value
+      display_error_unless( valid_email(email), 0 )
+  )
+  $('input[type="password"]').blur((evt) ->
+     password = evt.target.value
+     display_error_unless( password.length >= 8, 1 )
+     display_error_unless( password.match(/[A-Z]/), 2 )
+     display_error_unless( password.match(/\d/), 3 )
+  )
+  $('form[name="sign_in"]').submit((evt) ->
+    if $('.errors li').is(':visible')
+        evt.preventDefault()
+        return false
+    return true
+  )
+)