ngMessage is a directive with the purpose to show and hide a particular message.
For ngMessage to operate, a parent ngMessages directive on a parent DOM element
must be situated since it determines which messages are visible based on the state
of the provided key/value map that ngMessages listens on.
<!-- using attribute directives -->
<ANY ng-messages="expression">
  <ANY ng-message="keyValue1">...</ANY>
  <ANY ng-message="keyValue2">...</ANY>
  <ANY ng-message="keyValue3">...</ANY>
</ANY>
<!-- or by using element directives -->
<ng-messages for="expression">
  <ng-message when="keyValue1">...</ng-message>
  <ng-message when="keyValue2">...</ng-message>
  <ng-message when="keyValue3">...</ng-message>
</ng-messages>
Click here to learn more about ngMessages and ngMessage.
| Param | Type | Details | 
|---|---|---|
| ngMessage | string | a string value corresponding to the message key. |