Flattening an Array of Arrays with reduce()

Flattening an array of arrays is a common task in programming. It involves taking multiple arrays and combining them into a single array. This can be useful when working with data that consists of multiple nested arrays. In this tutorial, we’ll learn how to use the reduce() method to flatten an array of arrays.

What is reduce()?

The reduce() method is a method that is used to reduce an array of values into a single value. It takes a callback function as an argument, which is used to transform the array elements into a single value. This single value can be of any type, such as a number, string, or object.

How to Use reduce() to Flatten an Array of Arrays

To flatten an array of arrays with reduce(), we can use the spread operator to combine the arrays. We’ll use the reduce() method to iterate over each array and spread the values into a new array. Here is an example of how to use reduce() to flatten an array of arrays:

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let arr = [[1,2,3], [4,5,6], [7,8,9]];

let flattenedArr = arr.reduce((acc, val) => {
  return [...acc, ...val];
}, []);

console.log(flattenedArr); // [1,2,3,4,5,6,7,8,9]

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In the example above, we have an array of arrays called arr. We use the reduce() method to iterate over each array and spread the values into a new array. The reduce() method takes two arguments: an accumulator and a value. The accumulator is used to store the values from each iteration, and the value is the current array from the iteration. We use the spread operator to spread the values from the current array into the accumulator. The reduce() method returns the flattened array, which is then printed to the console.

Conclusion

In this tutorial, we learned how to use the reduce() method to flatten an array of arrays. We used the spread operator to combine the arrays and the reduce() method to iterate over each array. We then used the spread operator to spread the values from each array into the accumulator. This allowed us to reduce the array of arrays into a single flattened array.