Tutorials

Lodash _.groupBy() Collection Method

Posted in lodash Tutorial

Updated on Feb 24, 2024

By Mari Selvan

👁️ 96 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

Array manipulation in JavaScript often involves grouping elements based on specific criteria, and this is where the Lodash library shines. Among its arsenal of utility functions, the _.groupBy() method stands out as a powerful tool for grouping elements of an array based on a provided iteratee function.

Whether you're working with complex data structures or aiming to streamline data analysis, _.groupBy() proves to be an invaluable asset.

🧠 Understanding _.groupBy()

The _.groupBy() method in Lodash facilitates the grouping of elements in a collection based on a specified criterion. This criterion is defined by an iteratee function, allowing developers to tailor the grouping logic according to their unique requirements. The result is a new object where keys represent the groups and values are arrays containing elements that share the same group.

💡 Syntax

syntax.js

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_.groupBy(collection, [iteratee])

collection: The collection to iterate over.
iteratee (Optional): The function invoked per iteration.

📝 Example

Let's dive into a practical example to understand the functionality of _.groupBy():

example.js

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const _ = require('lodash');

const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9];
const groupedByOddEven = _.groupBy(numbers, num => (num % 2 === 0 ? 'even' : 'odd'));

console.log(groupedByOddEven);
/*
Output:
{
  odd: [1, 3, 5, 7, 9],
  even: [2, 4, 6, 8]
}
*/

In this example, the numbers array is grouped into two categories, 'odd' and 'even', based on the provided iteratee function.

🏆 Best Practices

Define a Clear Iteratee Function:

When using _.groupBy(), ensure that the iteratee function clearly defines the grouping logic. A well-defined iteratee function enhances code readability and makes the grouping criteria explicit.

example.js

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const people = [
  { name: 'Alice', age: 28 },
  { name: 'Bob', age: 32 },
  { name: 'Charlie', age: 28 },
];

const groupedByAge = _.groupBy(people, person => (person.age >= 30 ? 'above30' : 'below30'));

console.log(groupedByAge);
/*
Output:
{
  above30: [
    { name: 'Bob', age: 32 },
  ],
  below30: [
    { name: 'Alice', age: 28 },
    { name: 'Charlie', age: 28 },
  ]
}
*/

Handle Edge Cases:

Consider scenarios where the iteratee function might return undefined or null. Implement appropriate handling to ensure accurate grouping and avoid unexpected behavior.

example.js

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const items = [null, undefined, 1, 2, 3, 4, 5];

const groupedItems = _.groupBy(items, item => (item ? 'valid' : 'invalid'));

console.log(groupedItems);
/*
Output:
{
  invalid: [null, undefined],
  valid: [1, 2, 3, 4, 5]
}
*/

Utilize Object Keys:

Take advantage of the resulting object's keys for easy access to the groups. This can simplify subsequent operations or data retrieval.
example.js
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```
const fruits = ['apple', 'banana', 'orange', 'grape', 'apple'];

const groupedFruits = _.groupBy(fruits);

console.log(groupedFruits.apple);
// Output: ['apple', 'apple']
```

📚 Use Cases

Categorizing Data:

_.groupBy() is ideal for categorizing data based on specific attributes. Whether it's grouping products by category or users by region, this method streamlines the categorization process.

example.js

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const products = [
  { name: 'Laptop', category: 'Electronics' },
  { name: 'Coffee Maker', category: 'Appliances' },
  { name: 'Headphones', category: 'Electronics' },
];

const groupedProducts = _.groupBy(products, 'category');

console.log(groupedProducts);
/*
Output:
{
  Electronics: [
    { name: 'Laptop', category: 'Electronics' },
    { name: 'Headphones', category: 'Electronics' },
  ],
  Appliances: [
    { name: 'Coffee Maker', category: 'Appliances' },
  ]
}
*/

Data Analysis:

For data analysis tasks, _.groupBy() simplifies the process of aggregating and organizing data. It is particularly useful for generating summary reports or extracting meaningful insights.

example.js

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const salesData = [
  { product: 'Widget', revenue: 1200 },
  { product: 'Gadget', revenue: 800 },
  { product: 'Widget', revenue: 1500 },
];

const groupedByProduct = _.groupBy(salesData, 'product');

console.log(groupedByProduct);
/*
Output:
{
  Widget: [
    { product: 'Widget', revenue: 1200 },
    { product: 'Widget', revenue: 1500 },
  ],
  Gadget: [
    { product: 'Gadget', revenue: 800 },
  ]
}
*/

Streamlining UI Rendering:

When rendering dynamic content in a user interface, _.groupBy() can simplify the process by organizing data into groups, making it easier to iterate and display information efficiently.

example.js

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const tasks = [
  { id: 1, status: 'pending', description: 'Task 1' },
  { id: 2, status: 'completed', description: 'Task 2' },
  { id: 3, status: 'pending', description: 'Task 3' },
];

const groupedByStatus = _.groupBy(tasks, 'status');

console.log(groupedByStatus);
/*
Output:
{
  pending: [
    { id: 1, status: 'pending', description: 'Task 1' },
    { id: 3, status: 'pending', description: 'Task 3' },
  ],
  completed: [
    { id: 2, status: 'completed', description: 'Task 2' },
  ]
}
*/

🎉 Conclusion

The _.groupBy() method in Lodash empowers JavaScript developers to efficiently group elements in a collection based on a specified criterion. Whether you're categorizing data, performing data analysis, or streamlining UI rendering, _.groupBy() proves to be a versatile and essential tool in your array manipulation toolkit.

Explore the possibilities, enhance code readability, and simplify complex data manipulations with _.groupBy()!