What is the Expressions in Angular Js?

Expressions in AngularJS are snippets of code that are usually written within double curly braces {{ }} in HTML templates. These expressions are evaluated by AngularJS and replaced with their corresponding values or results in the rendered HTML.

Key Features of Expressions:
  1. Dynamic Content: Expressions allow you to display dynamic data in HTML templates.

                        <p>Hello, {{ username }}!</p>

  2. Simple JavaScript-Like Syntax: Expressions support JavaScript-like syntax and basic operations.

                        <p>Total: {{ quantity * price }}</p>

  3. Data Binding: Expressions facilitate two-way data binding, meaning changes in the model are automatically reflected in the view and vice versa.

                        <input type="text" ng-model="username">
                        <p>Hello, {{ username }}!</p>                    

  4. Usage with Directives: Expressions are commonly used with AngularJS directives for manipulating the DOM based on evaluated expressions.

                        <div ng-show="isLoggedIn">Welcome, {{ username }}!</div>

Characteristics and Limitations:
  • No Control Structures: Expressions are not meant to contain control structures like loops or conditionals. They are designed to be lightweight and are evaluated on the fly.
  • No Global Variables: Expressions can access properties/methods from the scope but don't have access to global JavaScript objects or functions.
  • Sanitization: AngularJS automatically sanitizes expressions to prevent injection attacks, ensuring security in the rendered output.
Example Usage:

Consider a simple example demonstrating expressions and data binding:

            <div ng-app="myApp" ng-controller="MyController">
                <input type="text" ng-model="username">
                <p>Hello, {{ username }}!</p>

            angular.module('myApp', [])
            .controller('MyController', ['$scope', function($scope) {
                $scope.username = 'John';

In this example, the value entered in the input field (bound to $scope.username) will be dynamically displayed in the paragraph (<p>Hello, {{ username }}!</p>) due to the AngularJS expression {{ username }}.

Expressions in AngularJS provide a simple yet powerful way to create dynamic and data-driven HTML templates, making it easier to bind and display data from the model to the view.

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