Скачать или смотреть How to Replace Values in an Array of Objects in JavaScript

Learn how to replace values in an array of objects using JavaScript without mutating the original array. Perfect guide for JavaScript beginners!
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Solving a Common JavaScript Problem: Replacing Values in an Array of Objects

JavaScript is a versatile and powerful programming language, often used for web development. However, like any tool, it can lead to challenges. One common problem developers face is modifying arrays of objects safely and effectively. In this guide, we will explore how to replace values in an array of objects with values from another array without modifying the original array.

The Problem Statement

Imagine you have an array of objects, called A, where each object contains properties. For instance:

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You also have a second array containing new values:

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The goal is to replace the x property in each object of array A with corresponding values from array B. The expected output should be:

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The Challenge

A common mistake is to simply create a reference to the original array, which can inadvertently modify A when you change values in the new variable. For instance, the following code will not yield the desired result:

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Why Does This Happen?

This occurs because of JavaScript's pass-by-reference behavior with objects. When you assign D = A, D is not a new array but a reference to A. Therefore, any modifications made to D will also affect A since they point to the same object in memory.

The Solution: Using the map Method

To prevent any unwanted changes to the original array, you can use the map method. This method allows you to create a new array by transforming every element of the original array. Here’s how you can implement it:

Step-by-Step Implementation

Use map to iterate over the array: The map function will process each element of A without altering the original array.

Destructure each object: Inside the map function, you can destructure the current object to access its properties.

Replace the x property with values from B: For each object, construct a new object with the updated x property using values from array B.

Here is how you can achieve this in code:

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Breakdown of the Code

A.map(...): This iterates over each object in A.

(el, i) =>: Uses an arrow function where el is the current object and i is its index.

({...el, x: B[i]}): This spreads the properties of the existing object el into a new object while replacing the x property with the corresponding value from B.

Conclusion

By using the map method in JavaScript to replace values in an array of objects, you can easily create a new modified array without altering the original. Not only does this prevent accidental mutations, but it also keeps your code clean and understandable. Remember, the key to working effectively with JavaScript arrays and objects is understanding how to manage references and copies. Happy coding!