Definition of AngularJS ng-disabled
AngularJS ng-disabled is an In-Built AngularJS directive that is used in the HTML view for disabling HTML elements such as input, select, button, etc. on a conditional basis by evaluating the expression defined in the ng-disabled directive. This directive comes into usage whenever the developer needs to add a disabled attribute in the HTML element but on some conditional basis or based on some criteria. If the expression inside ng-disabled evaluates to be TRUE then disabled attribute is added to that HTML element and if not then nothing is added. This can be used with HTML tag such as button, select, input, div, span, etc.
Syntax of AngularJS ng-disabled
There are various ways to write ng-disabled directive with different HTML Tags.
- Using ng-disabled with Input Type
<input type=”checkbox” ng-disabled=”conditionalDisabling” ng-model=”modelValue”></input>
- Using ng-disabled with Select Type
<select ng-disabled=”conditionalDisabling” ng-options=”reason as reason.desc for reason in reasonsList”></select>
- Using ng-disabled with Button Type
<button ng-model=”modelValue” type=”text” ng-disabled=” conditionalDisabling”>
- Using ng-disabled with div/span
<div ng-disabled=”conditionalDisabling” ng-click=”onClickOperation”> Update Request </div?
an ng-disabled directive can be used with multiple HTML element and can be used conditionally
How ng-disabled Directive Works in AngularJS?
In the AngularJS framework, it is very important to know that all the In-Built directive which have been provisioned by the AngularJS framework will always be denoted with ng prefix.
The ng-disabled directive is very simple and very easy to use the directive in the HTML view. This directive is used to disable any particular HTML element on the view based on conditional evaluation of the expression defined inside the ng-disabled directive. The way ng-disabled directive works are as soon as the HTML view come across ng-disabled directive declared in HTML elements, it evaluates the expression and if the value returned is TRUE then the disabled attribute is added to the same HTML element which disables that element. The ng-disabled attribute directive accepts any conditional binary or ternary expression as the value as well as it accepts any method call which is defined inside the controller and the controller can handle as per requirements and return a Boolean response. This ng-disabled directive can be used with select type, textarea, input types with checkbox, submit, div or span as well as with button HTML tags.
Using ng-disabled directive when the model value changes and expression inside ng-disabled uses model value then ng-disabled will get executed and update the disabled attribute accordingly Ng-disabled directive is executed at priority level 100 and as disabled attribute has few limitations as well in terms of interpolation that’s the reason ng-disabled came into the picture.
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Examples of AngularJS ng-disabled
Following are the examples as given below:
Example #1
Using ng-disabled with input type
Index.html
<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.3.15/angular.min.js"></script>
<script src="script.js"></script>
</head>
<body ng-app="disablingApp" ng-controller="disablingCtrl">
<h2>Billing Portal</h2>
<input type="checkbox" ng-model="mainCheckbox">Get the invoice details !!</input> <br> <br>
<input type="checkbox" ng-model="printCheckBox" ng-disabled="!mainCheckbox"> Print Bill </input> <br>
<input type="checkbox" ng-model="emailCardCheckBox" ng-disabled="!mainCheckbox"> Email Bill </input>
</body>
</html>
Script.js
var app = angular.module('disablingApp', []);
app.controller('disablingCtrl', function($scope) {
});
Above example shows how easily the ng-disabled directive can be used in AngularJS HTML view and tweaked around conditions as the developer wants to. This is an example of a Billing Portal where the user can select multiple options in order to receive the invoice details. The requirement is If the Use selects the option to receive Invoice details then the only User should be allowed to Select the mode of invoice bill i.e. does the user needs the bill of invoice or email of invoice or both. When the Get Invoice details option is not selected at that time we want the print and email checkboxes to be disabled. As soon as the Get Invoice details option is selected we want the Print and email checkbox to be enabled. As the model value will change the ng-disabled will get updated and will enable or disable the checkbox accordingly.
<input type="checkbox" ng-model="mainCheckbox">
Here simply a checkbox is added with ng-model.
<input type="checkbox" ng-model="printCheckBox" ng-disabled="!mainCheckbox">
Here we are adding the ng-disabled attribute which will be executed conditionally based on the model value of mainCheckbox. The model value mainCheckbox will get updated whenever the checkbox is selected or deselected.
Output:
Print and Email checkbox is disabled
Print and Email are enabled
Example #2
Index.html
<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.3.15/angular.min.js"></script>
<script src="script.js"></script>
</head>
<body ng-app="disablingApp" ng-controller="disablingCtrl">
<input type="checkbox" ng-model="allOptions">Select Checkbox to disable dropdown and button <br><br>
<select ng-options="color.key for color in colors" ng-model="selectedColor"
ng-disabled="allOptions">
</select><br><br>
<input type="submit" ng-disabled="allOptions"/>
</div>
</body>
</html>
Script.js
// Code goes here
var app = angular.module('disablingApp', []);
app.controller('disablingCtrl', function($scope) {
$scope.colors = [
{'key': 'Black', 'value': 'black'},
{'key': 'Red', 'value': 'red'},
{'key': 'Blue', 'value': 'blue'},
{'key': 'Light blue', 'value': 'cyan'},
{'key': 'Green', 'value': 'green'}];
});
Above example everything is same as above except that the ng-disabled is being now used to disable other fields based on its ng-model value and evaluation to TRUE or FALSE. As soon as the Checkbox is selected to disable all input fields on the HTML view this will disable all elements which have ng-disabled attribute added and who evaluation goes to true. This will add disabled attribute and will disable the fields.
Another Example for ng-disabled is to use ternary operators. Yes you heard it right, ng-disabled works perfectly if used with ternary operators in HTML view.
<input type="checkbox" ng-model="allOptions">
Here simply a checkbox is added with ng-model allOptions.
ng-disabled="allOptions"
Using conditions based on whether all options is selected or not and then disabling the dropdown and submit button.
Output:
When disable all checkbox is not selected
When checkbox is selected
Conclusion
ng-disabled is a directive in AngularJS which is mainly used to disable HTML elements in HTML view based on certain conditions. an ng-disabled directive is an In-Built AngularJS directive. There are various different forms of using this directive and proper syntax is all that is needed and you are ready to go.
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