Why does AngularJS include an empty option in select?

In AngularJS, when you use the ng-options directive to populate a <select> element, AngularJS may include an empty option if your model does not match any of the provided options or is set to a falsy/undefined value. This empty option typically looks something like:

<option value="?"></option>

Below, we’ll break down why this happens and how you can control or remove this behavior.

Why AngularJS Adds an Empty Option

Model-View Synchronization
AngularJS strives to keep your model (the data in your controller) in sync with your view (the rendered <select>). If the current model value does not match any of the options in the list, AngularJS inserts a placeholder option so the <select> remains valid and shows that no matching option is available.
Avoiding Browser Defaults
Without a placeholder, some browsers might auto-select the first item in the list, causing a mismatch between the displayed item and your actual model value (which is still undefined or doesn’t match). An empty option clarifies that there is no valid match for the current model state.
Better UX for Invalid or Uninitialized States
If the model is not yet set—say you’re waiting on data from an API—AngularJS keeps a blank slate in the <select> rather than forcing a default selection that might confuse users.

How to Manage or Remove the Empty Option

Use ng-model Properly
Make sure your ng-model is set to a value that actually matches one of the options defined in ng-options. If the model is supposed to be pre-populated, ensure it’s initialized in your controller.
Specify a “track by” Expression
In some scenarios, adding a track by clause can help AngularJS identify matching objects and avoid creating an empty option. For instance:
```
<select ng-model="selectedItem"
        ng-options="item.name for item in items track by item.id">
</select>
```
This ensures each item is uniquely identified by its id.
Provide a Custom “Empty” or Placeholder Option
If you want a more user-friendly placeholder, you can do something like:
```
<select ng-model="selectedItem"
        ng-options="item as item.name for item in items">
  <option value="">-- Select an item --</option>
</select>
```
Here, value="" indicates a manually defined placeholder, and AngularJS will typically not add its own if this matches your model’s uninitialized state.
Use ng-init or Controller Logic
Set your model to a valid item as soon as you know what the default should be. Once the model matches an existing option, AngularJS will remove the extra empty option.

Example

Controller:

angular.module('myApp', [])
  .controller('MainController', function($scope) {
    $scope.items = [
      { id: 1, name: 'Option A' },
      { id: 2, name: 'Option B' }
    ];
    
    // If selectedItem remains undefined, AngularJS may show a blank option
    $scope.selectedItem = $scope.items[0]; // Pre-select 'Option A'
  });

View:

<div ng-app="myApp" ng-controller="MainController">
  <select ng-model="selectedItem"
          ng-options="item as item.name for item in items track by item.id">
  </select>
</div>

If $scope.selectedItem is set to $scope.items[0] before the view renders, the first item will appear selected, and no extra empty option will be added.

Broader AngularJS & JavaScript Best Practices

Initialize Your Models: Make sure you give your model a default valid value if appropriate.
Track Uninitialized States: If you’re loading data asynchronously, display a separate loading message or a disabled state instead of leaving your model empty.
Dot Notation: If you’re manipulating nested objects, remember to use dot notation (e.g., user.selectedItem) to avoid scope inheritance issues.

Expand Your Skill Set

To fully master AngularJS (and any modern JavaScript framework), you’ll want a solid foundation in JavaScript and an understanding of how large-scale applications are designed:

Grokking JavaScript Fundamentals
Dive into crucial concepts like prototypes, closures, and asynchronous patterns to write cleaner, more efficient AngularJS code.
Grokking the System Design Interview
As your apps grow in scope, you’ll need system design fundamentals for performance, scalability, and robust architecture.

For real-time advice and practice, consider Coding Mock Interviews or System Design Mock Interviews. You can also explore free tutorials on the DesignGurus.io YouTube Channel.

Final Thoughts

AngularJS includes an empty option in <select> to ensure your uninitialized model or non-matching values are visibly reflected in the UI. It prevents conflicts between what the model says and what the user sees. If you initialize your model or provide your own placeholder, AngularJS typically won’t add its own empty option. By managing your model carefully and using directives like track by, you can build a clean, intuitive UI that keeps your model and view in perfect sync.

CONTRIBUTOR

TechGrind