Lodash _.sortedIndexBy() Array Method

Posted in lodash Tutorial

Updated on Feb 23, 2024

By Mari Selvan

👁️ 35 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

In the realm of JavaScript programming, efficient array manipulation is a common requirement.

The Lodash library comes to the rescue with a rich set of utility functions, and one such powerful tool is the _.sortedIndexBy() method. This method provides a convenient way to find the index at which an element should be inserted into a sorted array, based on a specified iteratee function.

🧠 Understanding _.sortedIndexBy()

The _.sortedIndexBy() method in Lodash is designed for situations where you have a sorted array and want to determine the position where a new element should be inserted while maintaining the array's order.

💡 Syntax

syntax.js

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_.sortedIndexBy(array, value, [iteratee=_.identity])

array: The sorted array to inspect.
value: The value to evaluate.
iteratee: The iteratee invoked for each element. The result of this function will be used for the comparison.

📝 Example

Let's delve into a practical example to grasp the functionality of _.sortedIndexBy():

example.js

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// Include Lodash library (ensure it's installed via npm)
const _ = require('lodash');

const sortedArray = [{ x: 10 }, { x: 20 }, { x: 30 }];
const newValue = { x: 25 };

const insertionIndex = _.sortedIndexBy(sortedArray, newValue, 'x');

console.log(insertionIndex);
// Output: 2

In this example, newValue is an object with a property x, and the sortedArray is an array of objects sorted based on their x property. The _.sortedIndexBy() method is used to find the index at which newValue should be inserted to maintain the sorted order.

🏆 Best Practices

Understand the Sorted Array:

Ensure that the input array is sorted before using _.sortedIndexBy(). If the array is not sorted, the result may be unpredictable.

example.js

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const unsortedArray = [3, 1, 4, 1, 5, 9, 2, 6, 5];

// Sorting the array
const sortedArray = _.sortBy(unsortedArray);
const insertionIndex = _.sortedIndexBy(sortedArray, 7);

console.log(insertionIndex);
// Output: 7

Choose an Appropriate Iteratee:

Select an iteratee function that correctly extracts the comparison value from each element. This is crucial for accurate positioning within the sorted array.

example.js

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const arrayOfObjects = [{ date: '2022-01-01' }, { date: '2022-02-01' }, { date: '2022-03-01' }];
const newObject = { date: '2022-02-15' };

const insertionIndex = _.sortedIndexBy(arrayOfObjects, newObject, obj => new Date(obj.date));

console.log(insertionIndex);
// Output: 2

📚 Use Cases

Maintaining Sorted Lists:

Use _.sortedIndexBy() when working with lists that need to be kept in a sorted order, such as maintaining an alphabetical or numerical ordering.

example.js

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const alphabeticalList = ['apple', 'banana', 'orange', 'strawberry'];
const newFruit = 'kiwi';

const insertionIndex = _.sortedIndexBy(alphabeticalList, newFruit);

console.log(insertionIndex);
// Output: 2

Efficient Searching in Sorted Data:

In scenarios where you have a large dataset sorted based on a specific property, _.sortedIndexBy() helps efficiently find the position for new elements.

example.js

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const sortedData = /* ...fetch data from API or elsewhere... */;
const newData = /* ...create or receive new data... */;

const insertionIndex = _.sortedIndexBy(sortedData, newData, 'timestamp');

console.log(insertionIndex);

🎉 Conclusion

The _.sortedIndexBy() method in Lodash is a valuable asset for JavaScript developers dealing with sorted arrays. Whether you are maintaining ordered lists or efficiently searching in large datasets, this method offers a clean and reliable solution.

Unlock the potential of array manipulation with _.sortedIndexBy() and explore the myriad possibilities it opens up for your JavaScript projects!