Скачать или смотреть How to Loop Through an Array in JavaScript and Retrieve All Items Efficiently

Learn how to properly loop through arrays in JavaScript and avoid common pitfalls that lead to losing data from earlier iterations.
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This video is based on the question https://stackoverflow.com/q/72253361/ asked by the user 'skander lassoued' ( https://stackoverflow.com/u/14071708/ ) and on the answer https://stackoverflow.com/a/72253412/ provided by the user 'cybering' ( https://stackoverflow.com/u/2121957/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

When working with arrays in JavaScript, especially when they contain objects, it’s common to want to extract data from each item for further processing. A frequent issue developers encounter is accidentally overwriting data during iteration. If you've ever found yourself only getting the last entry of your array, you're not alone! In this post, we’ll explore how to efficiently loop through an array and retrieve all its items without losing data.

The Problem

Let’s say you have an array of objects that contains various transaction logs. While attempting to loop through the array to retrieve data, you've noticed that you're only receiving results from the last object. Here’s a snippet of what your function may look like:

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In the code above, the result variable gets overwritten in each iteration, so at the end, it only holds the last resultData array.

The Solution

To fix this issue, we need to modify how we store the result of each iteration. Instead of overwriting the result variable, we can use it to collect all resultData entries throughout the loop. Here’s how to do it:

Step 1: Initialize an Empty Array

First, we need to initialize the result variable as an empty array at the beginning of the function:

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Step 2: Push Each Result into the Array

Update the loop so that instead of assigning item.resultData directly to result, we push this data into the array:

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

Final Function

Here’s how your modified getLogByTPE function would look like:

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

Conclusion

By simply initializing an empty array and using the push method, you can store all entries of your array during iteration. This practice not only helps in collecting the necessary data but also avoids common pitfalls that occur when overwriting values during array processing.

Now you can comfortably loop through arrays in JavaScript and gather all required data from objects without losing any entries! Happy coding!