How to Loop Through an Array of Objects Using *ngFor in Angular

Learn how to effectively loop through an array of objects using `*ngFor` in Angular, along with troubleshooting tips for common errors.
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How to Loop Through an Array of Objects Using *ngFor in Angular

Looping through an array of objects is a fundamental task in Angular when creating dynamic user interfaces. One commonly used directive in Angular is *ngFor, which allows developers to iterate over collections and render HTML elements based on the items in those collections. If you've encountered issues in this process, you're not alone! In this guide, we will address how to effectively use *ngFor to loop through an array and troubleshoot a common error related to passing clicked data to a function.

The Problem: Looping Through an Array of Objects

Let's say you have an array of objects structured as follows:

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

You want to display each merchantName as a button that, when clicked, will call a function to perform a specific action using the sn value of the clicked item.

Here’s the code for the buttons using *ngFor:

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

If you are facing issues where the list is not showing up correctly or you are receiving errors when clicking the button, let’s dive deeper to identify the solution.

Solution: Implementing *ngFor Correctly

Step 1: Check Your HTML Structure

Make sure your *ngFor directive is used correctly. Here’s an example structure you should follow:

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

Step 2: Correctly Declare the Array in Your Component

In your component, ensure that the data array is defined and properly initialized:

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

Step 3: Ensure Proper Syntax

One common mistake is forgetting to separate objects with commas in the array. Ensure that your array elements are properly formatted:

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

Step 4: Check the Click Function

Ensure the getTpeByUser function is defined in your component and accepts the right parameter. Here’s a simple structure for that function:

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

Step 5: Debugging Common Issues

No output from the list: If you see absolutely nothing on your page, make sure that your array is not empty and the variable holding it is correctly referenced in the template.

Error on button click: If you receive an error when clicking the button, verify the value being passed to the function. Check that the sn property exists on the objects in your array.

Conclusion

Using *ngFor to loop through an array of objects in Angular is straightforward once you ensure that your data structure, HTML syntax, and function logic are set up correctly. By following the steps above, you should be able to eliminate common problems and effectively display and interact with your data.

If you continue to face issues, take a closer look at the console for error messages, as they often provide clues on what might be going wrong.

Happy coding, and enjoy building your Angular applications!