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Learn how to use immediately invoked function expressions to set object properties in JavaScript effectively.
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This video is based on the question https://stackoverflow.com/q/67752842/ asked by the user 'Chris Barrett' ( https://stackoverflow.com/u/7703778/ ) and on the answer https://stackoverflow.com/a/67753056/ provided by the user 'trincot' ( https://stackoverflow.com/u/5459839/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Set Object Property Values Using Functions in JavaScript

When working with JavaScript, one common challenge developers face is setting the values of object keys using functions. This can be particularly challenging when trying to assign a computed value, such as a formatted date or concatenated string, directly into an object property. In this guide, we will explore a solution to a specific problem: how to set the value of the SORT object key using a function.

The Problem

Imagine you are generating an array of objects, where each object contains various properties including a unique identifier, a name, and a SORT key meant to hold a formatted value derived from the object’s name. Here’s an initial attempt at setting the SORT key using a function:

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However, when you run this code, the SORT property ends up containing the function itself rather than the return value from that function. This can leave you feeling stuck, but don't worry, there’s a straightforward solution!

The Solution: Immediately Invoked Function Expression (IIFE)

To achieve the desired effect of evaluating the function immediately during the object’s construction, you can utilize an Immediately Invoked Function Expression (IIFE). This concept allows you to execute a function as soon as it is defined. Here’s how you can implement it:

Step 1: Modify the SORT Property

Instead of assigning a function to SORT, wrap your function in parentheses and invoke it immediately like so:

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Step 2: Using padStart for Padding

Additionally, if you want a cleaner way to handle zero padding for single-digit values, JavaScript offers a handy method called padStart. You can enhance your SORT property like this:

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The Result

Using either of these approaches will ensure that the SORT property contains the computed value you expect, rather than a reference to the function itself. This small adjustment makes a significant difference in how your objects are constructed and used.

Conclusion

Setting object property values using functions in JavaScript can be a bit tricky if you're not familiar with some of the nuances of the language. However, by implementing an IIFE, you can easily compute and set the values as intended. This technique not only streamlines your code but also helps you avoid potential pitfalls associated with function references in object properties.

With this understanding, you're well-equipped to tackle similar challenges in your JavaScript projects. Happy coding!