Differences between ngIf and ngFor

"ngIf" and "ngFor" are two important directives in Angular, but they play different roles in manipulating and displaying data in the user interface.

ngIf

Purpose

"ngIf" is used to conditionally add or remove elements from the DOM based on a conditional expression.

Typical Usage

Useful when you want to render or not render a content block based on a condition.

Example

<div *ngIf="showBlock">
   Content to be displayed if showBlock is true.
</div>

Behavior

If the expression given to "ngIf" evaluates to "true", the element associated with "ngIf" is rendered in the DOM; otherwise, the element is removed from the DOM.

ngFor

Purpose

"ngFor" is used to iterate over a collection (like an array) and dynamically render elements in the DOM based on the items in that collection.

Typical Usage
Useful when you want to repeatedly create elements based on items in a collection.

Example

<ul>
   <li *ngFor="let item of listItems">
     {{item}}
   </li>
</ul>

Behavior

"ngFor" creates an associated element instance for each item in the collection, allowing dynamic display of repeated data.

In summary, "ngIf" is used to control the conditional display of elements based on a condition, while "ngFor" is used to iterate over a collection and dynamically create elements in the DOM based on the items in that collection. Both are powerful directives and are often used together to create dynamic and responsive user interfaces in Angular.