Disable submit button when form invalid with AngularJS

Selected response is correct, but someone like me, may have issues with async validation with sending request to the server-side - button will be not disabled during given request processing, so button will blink, which looks pretty strange for the users.

To void this, you just need to handle $pending state of the form:

<form name="myForm">
  <input name="myText" type="text" ng-model="mytext" required />
  <button ng-disabled="myForm.$invalid || myForm.$pending">Save</button>
</form>

You need to use the name of your form, as well as ng-disabled: Here's a demo on Plunker

<form name="myForm">
    <input name="myText" type="text" ng-model="mytext" required />
    <button ng-disabled="myForm.$invalid">Save</button>
</form>

To add to this answer. I just found out that it will also break down if you use a hyphen in your form name (Angular 1.3):

So this will not work:

<form name="my-form">
    <input name="myText" type="text" ng-model="mytext" required />
    <button ng-disabled="my-form.$invalid">Save</button>
</form>