Tutorials

Lodash _.sumBy() Math Method

Posted in lodash Tutorial

Updated on Oct 30, 2024

By Mari Selvan

👁️ 69 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

Efficiently handling numerical data is a common requirement in JavaScript programming. Lodash, a powerful utility library, provides a variety of functions to streamline array manipulation, and one such gem is the _.sumBy() method.

This method simplifies the process of calculating the sum of a specific property in an array of objects, making it an invaluable tool for developers dealing with datasets.

🧠 Understanding _.sumBy() Method

The _.sumBy() method in Lodash is designed for summing the values of a specific property in an array of objects. This can be particularly useful when working with datasets where you need to aggregate numerical values based on a common attribute.

💡 Syntax

The syntax for the _.sumBy() method is straightforward:

syntax.js

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_.sumBy(collection, [iteratee=_.identity])

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

📝 Example

Let's dive into a simple example to illustrate the usage of the _.sumBy() method:

example.js

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const _ = require('lodash');

const expenses = [
  { category: 'utilities', amount: 100 },
  { category: 'groceries', amount: 150 },
  { category: 'utilities', amount: 80 },
];

const totalUtilitiesExpense = _.sumBy(expenses, 'amount');

console.log(totalUtilitiesExpense);
// Output: 180

In this example, the expenses array is processed by _.sumBy() to calculate the total sum of the 'amount' property.

🏆 Best Practices

When working with the _.sumBy() method, consider the following best practices:

Validate Input Data:

Before applying _.sumBy(), ensure that the input data is valid and contains the expected properties. This helps prevent unexpected results or errors.

example.js

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const invalidData = [
  { item: 'apple', price: 1 },
  { item: 'banana' }, // Missing 'price' property
  { item: 'orange', price: 2 },
];

const totalInvalidData = _.sumBy(invalidData, 'price');
console.log(totalInvalidData);
// Output: NaN (due to missing 'price' property)

Provide a Default Value for Missing Properties:

To handle cases where the specified property is missing in some objects, provide a default value or handle such scenarios gracefully.

example.js

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const dataWithMissingProperties = [
  { product: 'laptop', price: 1200 },
  { product: 'mouse' }, // Missing 'price' property
  { product: 'keyboard', price: 50 },
];

const totalWithDefault = _.sumBy(dataWithMissingProperties, obj => obj.price || 0);
console.log(totalWithDefault);
// Output: 1250

Utilize Custom Iteratee Function:

Use the iteratee parameter to apply a custom function for extracting values from each object. This allows for more complex calculations based on specific criteria.

example.js

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const salesData = [
  { product: 'phone', revenue: 800, unitsSold: 2 },
  { product: 'tablet', revenue: 500, unitsSold: 1 },
  { product: 'laptop', revenue: 1200, unitsSold: 3 },
];

const totalRevenue = _.sumBy(salesData, obj => obj.revenue * obj.unitsSold);
console.log(totalRevenue);
// Output: 4400

📚 Use Cases

Total Expenses Calculation:

_.sumBy() is particularly useful when you need to calculate the total sum of a specific property, such as 'amount' in a collection of expenses.

example.js

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const expenses = [
  { category: 'utilities', amount: 100 },
  { category: 'groceries', amount: 150 },
  { category: 'utilities', amount: 80 },
];

const totalUtilitiesExpense = _.sumBy(expenses, 'amount');
console.log(totalUtilitiesExpense);
// Output: 180

Sales Revenue Aggregation:

In scenarios where you have data on sales with revenue and units sold, _.sumBy() can be employed to calculate the total revenue by multiplying these values.

example.js

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const salesData = [
  { product: 'phone', revenue: 800, unitsSold: 2 },
  { product: 'tablet', revenue: 500, unitsSold: 1 },
  { product: 'laptop', revenue: 1200, unitsSold: 3 },
];

const totalRevenue = _.sumBy(salesData, obj => obj.revenue * obj.unitsSold);
console.log(totalRevenue);
// Output: 4400

Statistical Analysis:

For datasets requiring statistical analysis, _.sumBy() can be part of a broader set of calculations to derive insights from numerical properties.
example.js
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```
const dataForAnalysis = /* ...fetch numerical data... */;

const total = _.sumBy(dataForAnalysis, 'value');
console.log(total);
```

🎉 Conclusion

The _.sumBy() method in Lodash provides a straightforward and efficient solution for calculating the sum of a specific property in an array of objects. Whether you're managing expenses, sales data, or conducting statistical analysis, this method empowers developers to perform numerical aggregations with ease.

By adhering to best practices and exploring diverse use cases, you can harness the full potential of the _.sumBy() method in your Lodash projects.