In modern web development, applying dynamic styles based on certain conditions is a common requirement. Angular provides a powerful directive called ngClass that allows developers to add, remove, or toggle CSS classes on an element based on expressions. In this article, we will explore how to use the ngClass directive to add conditional classes to your Angular application.

Understanding ngClass

The ngClass directive is an Angular built-in directive that enables you to dynamically add or remove CSS classes on an element based on specified conditions. It can be used with various types of expressions, such as strings, objects, or arrays.

Using ngClass with Strings

To add a single class conditionally using ngClass, you can use the following syntax:

htmlCopy code<div [ngClass]="'your-class'"></div>

However, this will add the class unconditionally. To make it conditional, you can use the ternary operator:

htmlCopy code<div [ngClass]="condition ? 'class-if-true' : 'class-if-false'"></div>

Replace condition with an expression that evaluates to a boolean value, and change class-if-true and class-if-false with the desired class names.

Using ngClass with Objects

Using ngClass with an object allows you to define multiple classes with their respective conditions in a single expression:

htmlCopy code<div [ngClass]="{ 'class-1': condition1, 'class-2': condition2 }"></div>

Here, condition1 and condition2 are expressions that evaluate to boolean values. If condition1 is true, the class-1 will be added to the element; if condition2 is true, the class-2 will be added to the element.

Using ngClass with Arrays

You can also use ngClass with an array to conditionally apply multiple classes:

htmlCopy code<div [ngClass]="['class-1', condition ? 'class-2' : 'class-3']"></div>

In this example, the class-1 will always be applied, while the class-2 or class-3 will be applied based on the condition value.


  1. Toggling a class based on a boolean property:
htmlCopy code<button [ngClass]="{ 'active': isActive }">Toggle Class</button>
  1. Applying different classes based on a user role:
htmlCopy code<div [ngClass]="userRole === 'admin' ? 'admin-class' : 'user-class'">User Content</div>
  1. Combining object and array syntax for complex conditional classes:
htmlCopy code<div
    { 'class-1': condition1, 'class-2': condition2 },
    condition3 ? 'class-3' : 'class-4'


The ngClass directive in Angular provides a flexible and powerful way to add, remove, or toggle CSS classes on elements based on various conditions. By understanding the different ways to use ngClass with strings, objects, and arrays, you can create dynamic and responsive user interfaces that adapt to the changing state of your application.

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