How to Properly Sum Objects Retrieved from the SharePoint API Using Angular and TypeScript

Learn how to resolve issues when summing up object values retrieved from the SharePoint API. We'll break down common mistakes and provide a clear solution using Angular and TypeScript.
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Troubleshooting and Summing Objects from the SharePoint API in Angular

When working with data from the SharePoint API in Angular, one of the common tasks is to sum up values from the retrieved objects. If you've encountered problems trying to achieve this, you’re not alone! In this post, we’ll discuss a common issue where developers encounter a NaN (Not a Number) when trying to sum values, and we will also provide a clear solution to get you back on track.

The Problem

Imagine that you've pushed multiple objects into an array after retrieving them from the SharePoint API. When you attempt to sum their values, you see NaN in your console. Here's a snippet of your original code to illustrate the situation:

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

While you believe everything is set up correctly, you'll soon find that the implementation has some issues that lead to unintended results.

Common Issues in Your Code

1. Incorrect Type Declaration

You used Number instead of number in your type declaration. In TypeScript, number is the primitive type you need for numerical values. This confusion may lead to unexpected results down the line.

2. Adding a Type to an Array

When you tried to push {dataTotal: Number} to your AssociateArray, you were essentially adding an object with an empty type, which is not helpful. Instead of a valid object to sum, you're trying to sum a type reference.

3. Inefficient Summation Method

Using a forEach() loop to sum the values can be improved by using the reduce() method which is cleaner and more efficient for this task.

The Solution

Given the identified issues, let’s revamp your code with a clearer approach to summation. Here’s how you should change the code:

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

Breakdown of the Solution

Use the Correct Type Declaration: Make sure that whenever you are working with numerical values, you use number and not Number.

Directly Use the Retrieved Data: There’s no need to create a new array unless you’re transforming the data. Use dataTotal directly in the reduce() call.

Leverage the reduce() Method:

This method takes two arguments: an accumulator (previous value) and the current object.

It iterates through each object in the array, accumulating the sum based on a specified property (in this case, value).

The second argument to reduce() initializes the sum at 0.

Example Scenario

Now, let’s say you have data points like this from your API response:

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

After applying the revised code, your associateSum would correctly log 60.

Conclusion

Summing values from objects retrieved via the SharePoint API doesn’t have to be daunting. By correcting type declarations, avoiding unnecessary array manipulations, and using the powerful reduce() method, you can efficiently and effectively manage your data. Keep practicing, and soon you will be more comfortable working with Angular and TypeScript!

If this guide helped you solve your issue or raised new questions, feel free to share your thoughts or ask for further clarification in the comments!