JavaScript Array from() Method

Posted in JavaScript Tutorial

Updated on Oct 06, 2024

By Mari Selvan

👁️ 32 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

The JavaScript from() method is a versatile tool that allows you to create arrays from array-like objects, iterables, or even map functions to transform and map elements.

In this comprehensive guide, we'll explore the syntax, usage, best practices, and practical use cases of the from() method to harness its full potential in your JavaScript projects.

🧠 Understanding from() Method

The from() method is used to create a new, shallow-copied array instance from an array-like or iterable object. It also accepts an optional mapping function, providing flexibility in transforming elements during array creation.

💡 Syntax

The syntax for the from() method is straightforward:

syntax.js

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Array.from(arrayLike[, mapFunction[, thisArg]]);

arrayLike: The array-like or iterable object to convert to an array.
mapFunction (optional): A function to call on each element of the array.
thisArg (optional): An object to use as this when executing the mapFunction.

📝 Example

Let's delve into a basic example to illustrate the usage of the from() method:

example.js

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// Convert a string to an array
const greeting = 'Hello, World!';
const charArray = Array.from(greeting);

console.log(charArray);  // Output: ['H', 'e', 'l', 'l', 'o', ',', ' ', 'W', 'o', 'r', 'l', 'd', '!']

Here, the from() method is used to transform the characters of the string greeting into an array.

🏆 Best Practices

When working with the from() method, consider the following best practices:

Handling Non-Array Iterables:

Ensure compatibility with non-array iterables by using the map function to convert elements appropriately.

example.js

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const set = new Set(['apple', 'orange', 'banana']);

const arrayFromSet = Array.from(set, fruit => fruit.toUpperCase());
console.log(arrayFromSet);  // Output: ['APPLE', 'ORANGE', 'BANANA']

Avoiding Pitfalls with Objects:

Be cautious when using from() with objects, as it might not behave as expected. If you need to convert object values into an array, consider using Object.values(obj).

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const obj = { a: 1, b: 2, c: 3 };
const arrayFromObj = Array.from(obj);  // Not recommended for objects
console.log(arrayFromObj);  // Output: []

const valuesArray = Object.values(obj);
console.log(valuesArray);  // Output: [1, 2, 3]

📚 Use Cases

Mapping Elements during Array Creation:

The from() method allows you to apply a mapping function during array creation, providing a concise way to transform elements:
example.js
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```
const numbers = [1, 2, 3, 4, 5];
const squaredArray = Array.from(numbers, num => num * num);

console.log(squaredArray);  // Output: [1, 4, 9, 16, 25]
```

Creating Arrays from DOM Collections:

Convert a DOM NodeList into an array using from():

example.js

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const nodeList = document.querySelectorAll('.list-item');
const arrayFromNodeList = Array.from(nodeList);

console.log(arrayFromNodeList);  // Array containing elements from the NodeList