Tutorials

Lodash _.forEachRight() Collection Method

Posted in lodash Tutorial

Updated on Feb 24, 2024

By Mari Selvan

👁️ 30 - Views

⏳ 4 mins

💬 1 Comment

Lodash _.forEachRight() Collection Method

Photo Credit to CodeToFun

🙋 Introduction

In the vast landscape of JavaScript, effective iteration over collections is a common necessity. Lodash, a powerful utility library, provides a variety of methods to streamline these tasks. Among them, the _.forEachRight() method stands out, offering a convenient way to iterate over elements in reverse order.

This method proves invaluable for scenarios where processing elements in a collection from the end to the beginning is crucial.

🧠 Understanding _.forEachRight()

The _.forEachRight() method in Lodash is tailored for iterating over elements in a collection, such as arrays or objects, in reverse order. It executes a provided function once for each element, providing a flexible and intuitive way to perform operations on the elements.

💡 Syntax

syntax.js

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_.forEachRight(collection, iteratee)

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

📝 Example

Let's explore a practical example to illustrate the functionality of _.forEachRight():

example.js

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const _ = require('lodash');

const numbers = [1, 2, 3, 4, 5];

_.forEachRight(numbers, (value, index) => {
    console.log(`Element at index ${index}: ${value}`);
});

In this example, the _.forEachRight() method is used to iterate over the numbers array in reverse order, logging each element along with its index.

🏆 Best Practices

Reverse Iteration:

Leverage _.forEachRight() when the order of iteration matters, and processing elements from the end to the beginning is essential.

example.js

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const words = ['apple', 'banana', 'orange'];

_.forEachRight(words, word => {
    console.log(word.split('').reverse().join(''));
});
// Output: "egap", "ananab", "egnaro"

Modifying the Original Collection:

Exercise caution when modifying the original collection inside the iteratee function to avoid unexpected behavior.

example.js

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

_.forEachRight(items, (value, index, collection) => {
    if (value % 2 === 0) {
        // Remove even numbers from the original array
        collection.splice(index, 1);
    }
});

console.log(items);
// Output: [5, 3, 1]

Utilizing Index Parameter:

Take advantage of the optional index parameter provided to the iteratee function when the index of the element is needed during processing.

example.js

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const colors = ['red', 'green', 'blue'];

_.forEachRight(colors, (color, index) => {
    console.log(`Color at position ${index}: ${color}`);
});
// Output: "Color at position 2: blue", "Color at position 1: green", "Color at position 0: red"

📚 Use Cases

Reversing Array Elements:

_.forEachRight() is useful when you need to process array elements in reverse order, which is common in scenarios like reversing strings or arrays.

example.js

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const originalArray = [1, 2, 3, 4, 5];
const reversedArray = [];

_.forEachRight(originalArray, value => {
    reversedArray.push(value);
});

console.log(reversedArray);
// Output: [5, 4, 3, 2, 1]

Removing Elements Conditionally:

When you want to remove elements from an array based on a condition, _.forEachRight() allows you to do so while maintaining correct indices.

example.js

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const numbersToRemove = [1, 2, 3, 4, 5];
const condition = number => number % 2 === 0;

_.forEachRight(numbersToRemove, (value, index, collection) => {
    if (condition(value)) {
        collection.splice(index, 1);
    }
});

console.log(numbersToRemove);
// Output: [5, 3, 1]

Processing Object Properties:

Iterating over object properties in reverse order can be achieved using _.forEachRight(), providing flexibility in property processing.

example.js

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const person = {
    name: 'John',
    age: 30,
    city: 'New York',
};

_.forEachRight(person, (value, key) => {
    console.log(`${key}: ${value}`);
});
// Output: "city: New York", "age: 30", "name: John"

🎉 Conclusion

The _.forEachRight() method in Lodash offers a convenient and efficient way to iterate over elements in reverse order within a collection. Whether you need to reverse array elements, conditionally remove elements, or process object properties in reverse, this method provides a versatile solution for diverse iteration needs in JavaScript.

Enhance your collection iteration experience with _.forEachRight() and unlock new possibilities in your JavaScript development!