Скачать или смотреть How to Check if a Variable Exists in an Object in JavaScript

Learn how to effectively check if a variable exists in a JavaScript object and retrieve its location. Follow our step-by-step guide for a clear understanding.
---
This video is based on the question https://stackoverflow.com/q/67231677/ asked by the user 'PHV' ( https://stackoverflow.com/u/9664966/ ) and on the answer https://stackoverflow.com/a/67231752/ provided by the user 'Shubham Periwal' ( https://stackoverflow.com/u/7608589/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How can I check if my variable exists in an object?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Check if a Variable Exists in an Object in JavaScript: A Simple Guide

When working with objects in JavaScript, one common task is determining whether a specific variable exists within that object. This can be particularly useful when you need to ensure data integrity or handle operations based on existing values. In this post, we will explore how to effectively check if a variable exists in an object and return its index, using a straightforward example.

The Problem at Hand

Let's say you have an object called data that looks something like this:

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

In this case, you want to check if a variable named articleNumber has a value of "ART0001" and determine its location within the data object. Your initial attempt might look something like this:

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

However, this approach returns -1, indicating that the value was not found. This result can be confusing, so let's uncover why this happens and how you can correct it.

Understanding the Issue

The problem arises because the Object.values(data) method returns an array of the values in the objects, but you're trying to search for a string directly within this array. The indexOf method won't work for finding properties within objects, especially nested properties.

The Solution

To effectively check if the value exists within the objects in your array, you can use the findIndex method. This method will search through each object in the array and allow you to define a condition that identifies the specific value you're looking for. Here's how you can do it:

Using findIndex

You can use the following code to check for the existence of articleNumber:

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

Explanation of the Code

findIndex: This method will iterate over each element of the data array.

Callback Function: The function (ele) => ele.ArticleNumber === "ART0001" checks if the ArticleNumber of the current element (ele) matches "ART0001".

Return Value: If a match is found, findIndex will return the index of that element; if not, it will return -1.

Example Usage

Putting it all together, here’s a complete example for your reference:

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

Conclusion

In summary, when you need to check if a variable exists within an object and find its index, instead of using Object.values and indexOf, you should opt for the findIndex method. This approach is more suitable for dealing with complex objects and ensures that you get the correct index for your search. Happy coding!