Concatenate form values in controller - angularjs

Question

I have a typical contact form where I concat the values into a preview div with AngularJS. This works fine if all the fields are filled out. I would like to move this into a controller so that I can conditionally add some static text such as only put a slash between phone and fax if both those fields are filled. I cannot find any sample code that goes beyond concatenating a couple values.
<div class="col-md-offset-1">
<div class="form-group">
<label class="control-label col-sm-2" for="companyFirm">Company/Firm</label>
<div class="col-sm-10">
<input type="text" ng-model="companyFirm" class="form-control" placeholder="Enter your company or firm name" required>
</div>
</div>
<div class="form-group">
<label class="control-label col-sm-2" for="contact">Contact</label>
<div class="col-sm-10">
<input type="text" ng-model="contact" class="form-control" placeholder="Enter the full name of the listing contact">
</div>
</div>
<div class="form-group">
<label class="control-label col-sm-2" for="address">Address</label>
<div class="col-sm-10">
<input type="text" ng-model="address" class="form-control" placeholder="Enter your street address">
</div>
</div>
<div class="form-group">
<label class="control-label col-sm-2" for="city">City</label>
<div class="col-sm-10">
<input type="text" ng-model="city" class="form-control" placeholder="Enter your city">
</div>
</div>
<div class="form-group">
<label class="control-label col-sm-2" for="state">State</label>
<div class="col-sm-4">
<input type="text" ng-model="state" class="form-control" placeholder="Enter your state">
</div>
<!-- </div>
<div class="form-group"> -->
<label class="control-label col-sm-2" for="phone">Phone</label>
<div class="col-sm-4">
<input type="phone" ng-model="phone" ng-change="getPhoneFax()" class="form-control" placeholder="Enter your phone number">
</div>
</div>
<div class="form-group">
<label class="control-label col-sm-2" for="zipcode">Zip Code</label>
<div class="col-sm-4">
<input type="text" ng-model="zipcode" class="form-control" placeholder="Enter your Zip Code">
</div>
<!-- </div>
<div class="form-group"> -->
<label class="control-label col-sm-2" for="fax">Fax</label>
<div class="col-sm-4">
<input type="phone" ng-model="fax" class="form-control" placeholder="Enter your fax number">
</div>
</div>
<div class="form-group">
<label class="control-label col-sm-2" for="email">Email</label>
<div class="col-sm-10">
<input type="text" ng-model="email" class="form-control" placeholder="Enter your email address">
</div>
</div>
<div class="form-group">
<label class="control-label col-sm-2" for="website">Website</label>
<div class="col-sm-10">
<input type="text" ng-model="website" class="form-control" placeholder="Enter your website address">
</div>
</div>
</div>
<h4>60-word Description</h4>
<div class="col-md-offset-1">
<div class="form-group">
<label class="control-label col-sm-2" for="description"></label>
<div class="col-sm-10">
<div>You have used <span class="wordCount">{{description|wordCounter}}</span> of your allowed 60 words.</div>
<textarea ng-model="description" class="form-control" rows="4" required></textarea>
<span class="help-block">Your 60 word, plain text only description begins after the listing header. You will receive a proof for approval prior to publication.</span>
</div>
</div>
<div class="col-md-offset-3 col-sm-6" style="background:#ddd; padding:15px; margin-top:50px;">
<strong>Live preview of listing</strong>
<div style="background:#fff; border:5px solid #eee; padding:15px; line-height:1em;">
<strong><span class="text-uppercase" style="font-size:1.3em;" ng-show="companyFirm">{{companyFirm}}<br /></span>
<span ng-show="contact">{{contact}}<br /></span></strong>
<span style="font-weight:500;">
<span ng-show="address">{{address}}<br /></span>
<span ng-show="city">{{city}}, </span><span ng-show="state" class="text-uppercase">{{state}}</span> <span ng-show="zipcode">{{zipcode}}</span><br />
<span ng-show="phone">{{phone}} / </span><span ng-show="fax">Fax: {{fax}}<br /></span>
<span ng-show="email">{{email}}<br /></span>
<span ng-show="website">{{website}}<br /></span>
</span>
<span style="color:#787878;">{{description}}</span>
</div>
</div>
<div class="clearfix"></div>
</div>
http://plnkr.co/edit/1oqneNRXuTXhiqE7vKWw?p=catalogue

Answer 1

If I understand question correctly, in controller You can use standard js concatenate:
$scope.phoneFax = function() {
//You can also save result in variable;
return ($scope.phone ? $scope.phone : '')
+ ($scope.phone && $scope.fax ? ' / ' : '')
+ ($scope.fax ? 'Fax: ' + $scope.fax : '');
};
Template:
<span>{{phoneFax()}}</span>
Also you can make it directly in the template:
<span ng-show="phone">{{phone}}</span>
<span ng-show="fax && phone"> / </span>
<span ng-show="fax">Fax: {{fax}}<br /></span>