Angular JS: Validate form fields before submit

I suggest to use sub-forms. AngularJS supports putting one form inside another, and validity is propagated form lower form to upper;

Here is example: http://plnkr.co/edit/SruBmlGZZtbwiU8cktAp?p=preview

Here is some code so you can grasp the idea:

  <form name="myform" ng-init="step = 1">
    <div ng-show="step==1">
      <h3>Step 1: Enter some general info</h3>
      <div ng-form='step1form'>
        Name: <input ng-model="name" required>
      </div>
      <button ng-disabled="!step1form.$valid" ng-click="step = 2">Next</button>
    </div>

    <div ng-show="step==2">
      <h3>Step 2: Final info</h3>
      <div ng-form="step2form">
          Phone: <input ng-model="phone" required>
      </div>
      <button  ng-click="step = 1">Prev</button>
      <button ng-disabled="!myform.$valid" ng-click="submit()">Submit</button>
    </div>
    <div>
      Validation status:
      <div> Whole form valid? {{myform.$valid}} </div>
      <div> Step1 valid? {{step1form.$valid}} </div>
      <div> Step2 valid? {{step2form.$valid}} </div>
    </div>
  </form>