What are different states of a form in AngularJS?

Started by beingchinmay, 03-18-2017, 07:08:45

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beingchinmayTopic starter

The AngularJS form goes to the following states, starting from the form rendering and when the user has finished the filling of form.


TonyBalon

AngularJS (up to version 1.x) on its own doesn't differentiate "states" of a form like some newer frontend libraries or frameworks such as Angular 2+ or React do. However, AngularJS provides properties on form and form control objects to keep track of their interaction and validation states. These properties can be used to create "state"-like behaviors.

Below are the built-in AngularJS properties you could consider as relating to a form's "state":

$dirty: This flag becomes true when the user interacts with the form in any way.
$pristine: The opposite of $dirty. This is true if the user has not yet interacted with the form.
$valid: This property is true if all of the containing form controls are themselves valid.
$invalid: This is the opposite of $valid, so it's true if any form control within the form is invalid.
$touched: This property is true if the user has blurred the form control, meaning they've left the control after interacting with it.
$untouched: Opposite to $touched, this means the control hasn't been blurred yet.
$error: This object hash includes references to every invalid control in the form.
Further, AngularJS also provides mechanism to validate the forms on the basis of built-in directives like required, minlength, maxlength, ng-min, ng-max etc. and even custom validations can be built.

I'll expand on different ways these form properties are used if that helps:

Showing Validation State Feedback: We can use the above properties to give immediate feedback to the user as they fill out the form. For instance, if a certain field has $invalid and $touched both as true, it means that the user has interacted and left the field, but the input was invalid. Here, we could use this to show a red border around the invalid fields, or a text warning underneath it.

Disabling Submit Button: To prevent users from submitting an invalid form, we can disable the submit button until the form is valid. This can be done using the $invalid property on the form. e.g. in the submit button element, you could do something like <button type="submit" ng-disabled="myForm.$invalid">Submit</button>

Showing Error Messages: Errors can be shown using the $error object. This object contains keys corresponding to every validator that failed. So if you had a field with a required attribute that was empty, $error.required would be true. You can use this to show custom error messages related to each kind of validation. For example <div ng-show="myForm.myField.$error.required">This field is mandatory.</div>

Handling Form Submission: Once the form finally is $valid and user submits it, you can have AngularJS call a function in your controller to handle it. You can also pass in the form controller itself to inspect the form's state manually. For example: <form ng-submit="submitForm(myForm)" novalidate>.

AngularJS is a popular open-source JavaScript framework maintained by Google. Its primary purpose is to streamline Web application development, in particular single-page applications (SPAs). SPAs are web applications or websites that interact with the user by dynamically rewriting the current web page with new data from the web server, instead of default method of the browser loading entire new pages.

Key Features of AngularJS include:

Data Binding: AngularJS supports two-way data binding meaning the view and model layer of the application are always in sync. When data in the model changes, the view reflects the change, and vice versa.

Directives: Directives are markers on a DOM (Data Object Model) element (such as an attribute, element name, or CSS class) that tell AngularJS's HTML compiler to attach specified behavior to that DOM element or even transform it and its children. Some commonly used directives include ng-bind, ng-model, etc.

Controllers: A Controller is a JavaScript object containing attributes/properties and functions to control the behavior of the data. Each controller belongs to a particular AngularJS application defined by ng-app.

Scope: Scopes are objects that refer to the model. They act as a glue between controller and view and are arranged in a hierarchical structure which mimics the DOM structure of your app.

Services: AngularJS comes with several built-in services like $http to make a XMLHttpRequests. These are singleton objects which are instantiated only once in app.

Dependency Injection (DI): AngularJS has a built-in dependency injection subsystem that helps the developer by making the application easier to develop, understand, and test.

Routing: You can switch views by using the concept of Routing in AngularJS. The ngRoute module helps to use routing.

Templates: These are rendered view with information from the controller and the model. They can be a single or multiple views in one page using "partials".


let's dive a little deeper into some of the components of AngularJS and its usage:

Modules: An AngularJS module defines an application. A module is a container for the different parts of your application - controllers, services, filters, directives, etc. A standard way to set up an AngularJS application is by using the ng-app directive to define the application and the ng-controller directive to control the application.

Expressions: AngularJS expressions are written inside double braces: {{ expression }}. They behave very much like JavaScript expressions: they can contain literals, operators, and variables. For example, an expression could be {{ 5 + 5 }} or {{ firstName + " " + lastName }}.

Filters: Filters select from a subset of items in an array and returns a new array. Filters are used for formatting data displayed to the user. They can be used in view templates, controllers, services and directives. Some built-in filters include lowercase, uppercase, orderBy, filter, etc. Custom filters can also be created.

Services and Factories: While Services are constructor functions and are instantiated with the new keyword, AngularJS factories are functions which, if you choose, could return objects which would then be used as services. Both Services and Factories are used to organize and share code across your application.

Directives: Directives are markers on a DOM element (such as attributes, element name, comment or CSS class) that tell AngularJS's HTML compiler ($compile) to attach a specified behavior to that DOM element. AngularJS comes with several built-in directives like ngBind, ngModel, and ngClass. It's also possible to define your own custom directives.

Forms and Validation: AngularJS is also well-equipped to handle forms and form validation. It has directives for handling user input, like ng-model and ng-submit, and it provides feedback on form validation using classes and scope properties.

Testing: One of the reasons AngularJS is popular is because it's designed with testability in mind. It provides support for both Unit testing (with tools like Jasmine and Karma) and End-to-End testing (with tools like Protractor).


modern legacy of AngularJS.

Animations: AngularJS provides support for adding animations for various directives. The ngAnimate module provides support for CSS-based animations as well as JavaScript-based animations.

ng-include: The ng-include directive allows you to include HTML content from external HTML files. It's useful when dividing the application into multiple views and organizing the code in separate files.

httpService∗∗:OneofthemostusedfeaturesinAngularJSisthehttp service, which makes a request to the server, and then returns a response. Notably, it's used to retrieve data from some URL and then used it in controllers.

AJAX In AngularJS: AngularJS supports CRUD (Create, Read, Update, Delete) operations via $http service to make your application purely RESTful.

AngularJS is a comprehensive solution for building dynamic single-page applications and has become a standard for web development. Its popularity has given birth to an ecosystem filled with third-party modules, add-ons, and tools that extend AngularJS's potential even more.

The main differences between AngularJS and Angular include a shift from controllers to components structure, TypeScript being the main language, mobile development capabilities, dynamic loading, improved dependency injection, and more. The Angular team provides tools to help migrate an AngularJS app to Angular, but the process can be complex, especially for larger applications.

Still, AngularJS remains widely used for its simplicity and the broad pool of resources available. However, developers starting a new project should consider using Angular (2+) or assessing other modern frameworks such as React or Vue.js.
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