Conditional Rendering with ngIf in Angular

In Angular applications, dynamic content based on data or user interactions is essential. The ngIf structural directive provides a powerful way to conditionally include or exclude elements from the template, ensuring a seamless user experience.

Understanding ngIf

• Structural Directive: ngIf modifies the DOM structure by adding or removing elements based on a condition.
• Expression Binding: It takes an expression as input, typically a boolean value or one that evaluates to truthy or falsy.
• Conditional Rendering: When the expression is true, the element and its content are displayed. If it’s false, they’re removed from the DOM, optimizing performance.

<div *ngIf="isLoggedIn">
  Welcome back!
</div>

• The *ngIf directive is placed on a div.
• The expression isLoggedIn controls the visibility.
• If isLoggedIn is true, the welcome message with the username is displayed.
• Otherwise, the div and its content are hidden from the user.

example:

<div>
  <p *ngIf="value">The value is true.</p>
  <p *ngIf="!value">The value is false.</p>
</div>

In above code if the value is true, only display “The value is true”. Otherwise display “The value is false.”