How to Dynamically Increase Object Key Values in JavaScript

Описание: Learn how to manipulate object keys in JavaScript to dynamically increase their values using a variable key. Perfect for tasks involving data aggregation!
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This video is based on the question https://stackoverflow.com/q/70348335/ asked by the user 'John Doener' ( https://stackoverflow.com/u/17023379/ ) and on the answer https://stackoverflow.com/a/70348446/ provided by the user 'DustInComp' ( https://stackoverflow.com/u/11572498/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Dynamically Increase Object Key Values in JavaScript

When working with JavaScript, you might often encounter scenarios where you need to manipulate object values based on dynamic keys. A common challenge is incrementing the value of an object property when you don’t know the property names in advance. In this guide, we'll explore how to achieve this by breaking down a specific problem and presenting a clean solution.

The Problem You May Face

Let's say you have an object that tracks some scores, like this:

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Now, imagine you are dealing with data items that look like this:

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The goal is to increment the score in obj based on the who key of each data item. However, you may not know in advance what the values of who are (i.e., foo and bar). Therefore, directly checking with a condition like if (data.who === "foo") won't help. So, how can we dynamically update the value associated with these keys?

The Solution Breakdown

Step 1: Set Up Your Data Structure

First, let's set up an array to hold your data items. This will allow us to easily iterate over them later. You can define it like this:

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Here, tasks contains multiple objects that we want to process.

Step 2: Initialize the Result Object

Next, we need an empty object that will store our results, where each key corresponds to the who property, and the values will be the counts we want to increase:

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Step 3: Loop Through the Data Items

We can now loop through each item in the tasks array and update our obj based on the who key. Here’s how to do it using a simple for...of loop:

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In this loop:

data.who accesses the dynamic key you want to increment.

The syntax (obj[data.who] ?? 0) initializes the count to 0 if it’s undefined, then increments it by 1 regardless of whether it was previously set.

Alternative Approach with reduce

If you prefer a more functional programming approach, you can achieve the same result using the reduce method. Here’s how:

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In this code:

reduce iterates over each task and builds a new object counts.

It uses the spread operator ...counts to retain previous properties while adding or updating the data.who key dynamically.

Conclusion

Both methods—looping through the data or utilizing reduce—are effective for dynamically increasing the values of object keys in JavaScript based on variable keys. This technique is incredibly useful for data aggregation tasks where the keys are not predetermined, allowing for flexibility and scalability in your code.

Now you should be equipped to tackle similar challenges in your JavaScript projects. Happy coding!