How Can I Efficiently Generate Cartesian Products of Arrays in JavaScript?

Generating Cartesian Products of Arrays in JavaScript

Calculating the Cartesian product of multiple arrays is a common task in programming. It involves combining elements from each array to create new arrays containing all possible combinations. To achieve this in JavaScript, we can employ various approaches.

One simplistic but outdated approach requires iterating over each array and manually generating all possible combinations. However, this method becomes inefficient for large datasets. Instead, we can leverage advanced techniques in ES6 and ES2019 to significantly simplify the process.

Optimized 2020 Solution

With the introduction of flatMap in ES2019, we can reduce the Cartesian product calculation to a single concise line of code:

const cartesian = (...a) => a.reduce((a, b) => a.flatMap(d => b.map(e => [d, e].flat())));

Example Usage

To illustrate, let's consider the example provided in your question:

const output = cartesian([1, 2], [10, 20], [100, 200, 300]);

This command generates the following Cartesian product:

[
  [ 1, 10, 100 ],
  [ 1, 10, 200 ],
  [ 1, 10, 300 ],
  [ 1, 20, 100 ],
  [ 1, 20, 200 ],
  [ 1, 20, 300 ],
  [ 2, 10, 100 ],
  [ 2, 10, 200 ],
  [ 2, 10, 300 ],
  [ 2, 20, 100 ],
  [ 2, 20, 200 ],
  [ 2, 20, 300 ]
]

Conclusion

By embracing modern JavaScript features, we can tackle complex tasks like Cartesian product calculations with remarkable ease. Whether it's for algorithm development or data manipulation, these techniques empower developers to code more efficiently and elegantly.

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