Angularjs checkboxlist required validation with demo

Checkbox list at least one is required, checkbox list minimum 3 is required, gender at least one is required are the basic requirement for any situation. We will use the toggle trick to add remove the selected items from the list of checkbox values.

In this article we are going to see the examples:

1- Radiobutton list, at least one value is required 2- Checkbox list, at least one value is required 3- Checkbox list, at least three value is required 4- Checkbox list select all 5- Checkbox list clear all 6- Clear all checkbox on un-check of any checkbox

Gender Radio button list Simplest example of gender selection to select one of gender and make required until user select any one of gender:

<div>
  <label><input type="radio" 
    name= "gender" 
    value="Male" 
    ng-model="gender" 
    required /> Male</label>
</div>
<div>
  <label><input type="radio" 
    name= "gender" 
    value="Female" 
    ng-model="gender" 
    required  /> Female</label>
</div>

• name: We used here name to group the radio buttons to select only one item from group.
• value: every radio button will have unique value
• ng-model: it will be assigned on click/switching
• required: we can use either required or ng-required= "true"

Next we will use the check box list but the problem is, we cannot directly use above trick because in checkbox list we can select multiple items.

At least one checkbox in ng-repeat is required: Here we are going to use the trick toggling, means by default we will have a variable on scope to keep selected items as an array, either blank fir first time or some items in it in edit mode. On clicking any check box we will try to find the index of clicked item in selected array, if not exist then we add it otherwise we will remove it from the selected list. Let's see the code and then we can explain in detail:

In controller we have two variables on scope

$scope.selectedAnimals = [];
$scope.animals = ['Cat', 'Bear', 'Deer', 'Lion', 'Tiger'];

Now we need to create the list by using ng-repeat on animals, here is the HTML

<ul  class="list-group">
  <li ng-repeat='animal in animals' class="list-group-item">
    <label>
      <input type="checkbox"
        ng-model="xyx"
        ng-click="toggleAnimal(animal)"
        ng-checked="selectedAnimals.indexOf(animal) > -1"
        ng-required="selectedAnimals.length == 0" /> 
        {{animal}}</label>
  </li>                  
</ul>

• ngRepeat: Simply create the list of items
• ngModel: it is required for ng-required so give any name, it is only to stop the error that ng-required need the ng-model
• ngClick: this is the method we will use to add or remove the item from the selected list which we will see next
• ngChecked: Item will be check or un-checked on the basis of selected list
• ngRequired: if selected items count is 0 means no item is selected yet and it is required

Let's add the method chkSelectAnimals(animal)

$scope.toggleAnimal = function(animal){
    var index = $scope.selectedAnimals.indexOf(animal);
    if(index == -1) {
      $scope.selectedAnimals.push(animal);
    }
    else{
      $scope.selectedAnimals.splice(index, 1);
    }
}

This function accept a value, clicked item, in our case animal name, check the index of this item in selected list, if exist (greater than -1), remove it otherwise add to the list.

Checkbox list minimum 3 items are required, Select All Checkbox:

In this section we are going to see how to make N-number of items required, how we can use select all, clear all and on checking and unchecking items how we manage select all checkbox, say if all items selected one by one then all checkbox should be selected, on unchecking a checkbox, all checkbox should be un-checked.

Here we also use a list of color object and keep id of object on selection:

$scope.selectedColors = [];
$scope.colors = [
  {"id": 1, "color": "Red"},
  {"id": 2, "color": "Orange"},
  {"id": 3, "color": "Yellow"},
  {"id": 4, "color": "Green"},
  {"id": 5, "color": "Cyan"},
  {"id": 6, "color": "Blue"},
  {"id": 7, "color": "Indigo"}
];

Let's add HTML for "Select/Clear All" check box and checkbox list of colors from the above array we created, see this time we are using the array of object of colors and we will create the list of ids:

<label>
  <input type="checkbox" 
    ng-model="chkAll"
    ng-checked="colors.length === selectedColors.length"
    ng-click="selectAllColors()" > Select/Clear All</label>

<ul class="list-group">
 <li class="list-group-item" ng-repeat="item in colors">
   <label> 
     <input type="checkbox"
        ng-model="xyz"
        ng-checked="selectedColors.indexOf(item.id) > -1"
        ng-click="toggleColor(item.id)"
        ng-required="selectedColors.length < 3"> {{item.color}}</label> 
 </li>
</ul>

Select/Clear All: trick is simple, if all selected item count became equal to the list of colors (source list) items count, it will be checked otherwise un-checked by using the code ng-checked="colors.length === selectedColors.length". On clicking it, if checkbox is checked we select all otherwise clear the array, see this:

$scope.selectAllColors = function(){   
    if($scope.chkAll == true)
       $scope.selectedColors = $scope.colors.map(x=>x.id)
    else
      $scope.selectedColors = [];
}
// if you don't want to use the arrow function then use function like this
$scope.colors.map( function(x) {return x.id; })

Creating the list of checkbox is very same as our previous example except the number of required item are 3 now so ng-required="selectedColors.length < 3", means the number of selected item must be 3. See the rest of the code:

$scope.toggleColor = function(id){
   var index = $scope.selectedColors.indexOf(id);
   if(index == -1)
     $scope.selectedColors.push(id);
   else
     $scope.selectedColors.splice(index, 1);
}

We would love to help if you have any special case which can help others as well.

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