How to Create a New Array in TypeScript with Conditional Content Based on Object Properties

Learn how to efficiently create a new array in TypeScript using conditional logic based on the properties of existing object arrays. This guide walks you through a clear solution that highlights potential pitfalls.
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Creating a New Array in TypeScript Based on Object Properties

When working with arrays of objects in TypeScript, you may encounter scenarios where you need to create a new array from existing data with specific conditions applied. In this guide, we will walk you through a real-world example where we want to combine data from two arrays — userData and GroupData — to format a new result array with conditional content.

The Problem

In the given scenario, we have two arrays defined as follows:

userData: contains user information, including their associated groupId.

GroupData: includes group information, specifically userGroupId and their respective groups, identified by a type field.

Our goal is to create a new array that incorporates the data from userData, and adds the corresponding group name from GroupData under certain conditions:

If the groupId in userData matches userGroupId in GroupData, we want to include the group's name from the first group with type 1.

If no matching group with type 1 exists, we should set the content to null.

The Solution

Step 1: Define Your Data Structures

First, let's make sure we have our types defined properly for TypeScript. Here’s how we can define the types for clarity:

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

Step 2: Initialize Arrays

Next, set up the actual arrays according to the data provided:

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

Step 3: Create the New Array

Now, we can implement the logic to populate our new array. We can use the forEach method to iterate through userData and the find method to locate the relevant group from GroupData:

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

Explanation of the Logic

Iteration: We use forEach to loop through each user in userData.

Conditional Search: For each user, we apply find to catch the first matching entry in GroupData with both the same userGroupId and type of 1.

Null Handling: If a match is found, we extract the group; otherwise, we set content to null.

Array Population: We finally create a new object with the combined properties and push it into the resultArr.

Conclusion

This approach provides an efficient way to create a new array based on existing data with specific conditions in TypeScript. By defining types and using methods like forEach and find, we handle our data carefully, ensuring that we check conditions properly and avoid common errors — such as accessing properties that may not exist.

Now you can apply similar logic to your data manipulation tasks in TypeScript, simplifying your workflow significantly!