Introduction
Angular is a popular web development framework that allows developers to create robust single page applications (SPA) and complex web applications. One of the key features of Angular is the ability to iterate over an array or object and display the data using built-in directives. In this article, we are going to focus on the ngFor directive.

What is Angular ngFor directive?
The ngFor directive is a structural directive in Angular that allows developers to loop over an array or object and display the data. The ngFor directive is commonly used when working with data in a component or fetching data from an API. It is an essential feature of Angular as it helps generate dynamic content on the HTML template.

Syntax of ngFor directive
The syntax of ngFor directive is quite simple. Let’s take a look at the basic syntax.

“`

{{ item }}

“`

In the above syntax, *ngFor indicates that it is a structural directive, ‘let’ keyword is used to declare a variable ‘item’ and ‘items’ is the array that we are iterating over.

Using Index with ngFor directive
Sometimes we also need to keep track of the index of the current iteration. We can use the index keyword with ngFor directive for this purpose.

“`

{{ i }} : {{ item }}

“`

In the above syntax, ‘let i = index’ declares a variable ‘i’ of type number, which represents the current index of the iteration.

Using ngFor with Objects
In addition to array, the ngFor directive can also be used with objects. Let’s take a look at the syntax.

“`

{{ item.key }}: {{ item.value }}

“`

In the above syntax, we are using ‘let item of object’ to iterate over an object, where ‘item’ represents each key-value pair of the object.

Using ngFor with Nested Arrays and Objects
Sometimes, we may need to work with nested arrays or objects. Let’s take a look at the syntax.

“`

{{ item.title }}

  • {{ subitem.title }}

    • {{ sub_subitem.title }}

“`

In the above syntax, we are iterating over an array of objects, and each object has a nested array of objects. Each sub-array can also have a nested array of objects.

Using ngFor directive with ngSwitch directive
The ngFor directive is often used with other directives, such as the ngSwitch directive. The ngSwitch directive allows developers to conditionally render content based on a value. Let’s take a look at the syntax.

“`

{{ item.content }}

{{ item.alt }}

“`

In the above syntax, we are using ngSwitch directive inside the ngFor directive to conditionally render content.

FAQs

1. What is the difference between ngFor and ngRepeat?
NgFor is the directive use in Angular, whereas ngRepeat is used in AngularJS. The functionalities are quite similar; however, their syntax is different.

2. Can we use ngFor directive inside onClick event?
Yes, we can use ngFor directive inside onClick event. For instance, we can pass an argument to an event handler.

3. What is the maximum number of elements that can be shown using ngFor?
There are no restrictions on the number of elements displayed on the page using ngFor directive. However, it is recommended not to display too many elements as it may impact the performance of the application.

Conclusion
In conclusion, ngFor directive plays a vital role in generating dynamic content on the HTML template that is based on an array or object. It is an essential feature of Angular, enabling developers to iterate over arrays or objects efficiently. It has diverse functionalities that make it essential to use when working with data in an Angular application.

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