Скачать или смотреть How to Use *ngFor in Angular to Increment Index by Two

Learn how to use the Angular `*ngFor` directive for customizing index increments, easily displaying items at specific intervals like 0, 2, 4...
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Understanding Angular's *ngFor for Incrementing Index by Two

In Angular, the *ngFor directive is a powerful feature that enables developers to loop through collections and render elements within the template. However, you might encounter a scenario where you want to display items at specific index intervals—specifically, by incrementing the index by two (e.g., 0, 2, 4, 6...). In this guide, we will guide you through how to accomplish this effectively.

The Problem at Hand

Let’s say you have an array or a list of items, and you only want to display every second item. If you have a list that looks like [item1, item2, item3, item4, item5], the requirement is to show item1, item3, and item5. In typical programming languages like C, you could achieve this with a simple for loop that increments by 2. However, in Angular's template syntax, the implementation requires a slightly different approach.

The Solution: Using *ngFor with Conditional Rendering

To selectively display items based on an incrementing index, you can utilize the combination of *ngFor and an Angular structural directive called *ngIf. Here’s how to set it up:

Displaying Even Indices (0, 2, 4...)

If your objective is to display the items at even indices, you can structure your *ngFor loop as follows:

[[See Video to Reveal this Text or Code Snippet]]

Explanation:

*ngFor="let item of items; let i = index": This directive loops through the items array and provides both the item and the index (i).

*ngIf="i % 2 === 0": This condition checks if the index i is even. If true, it displays the item and its corresponding index.

Displaying Odd Indices (1, 3, 5...)

Conversely, if you want to display the items at odd indices, simply modify the condition inside *ngIf:

[[See Video to Reveal this Text or Code Snippet]]

Explanation:

Here, *ngIf="i % 2 !== 0" checks for odd indices, ensuring only items at indices 1, 3, 5, etc., are displayed.

Conclusion

Utilizing Angular's *ngFor directive in conjunction with conditional logic via *ngIf allows you to customize the display of array items based on their indices efficiently. Whether you need to show items at even or odd positions, this approach is clean and maintainable.

By using the code snippets provided, you can easily tailor your Angular applications to meet specific UI requirements. Keep exploring the capabilities of Angular to create even more dynamic and engaging applications!