JavaScript Array flat Method (Live Playground)

The JavaScript Array flat method is used to flatten an array, which means it converts a multi-dimensional array into a single-dimensional array.

Here's a basic example of how you can use the flat method:

let nestedArray = [1, [2, 3], [4, [5, 6]]];
let flattenedArray = nestedArray.flat();

console.log(flattenedArray);

// Expected output:
// [1, 2, 3, 4, [5, 6]]

In the example above, nestedArray.flat() creates a new array that's one level less nested than the original. The default depth that flat flattens is 1.

Live Playground, Try it Yourself

You can also specify the depth to which you want to flatten the array:

let deeplyNestedArray = [1, [2, [3, [4, [5]]]]];
let deeplyFlattenedArray = deeplyNestedArray.flat(4);

console.log(deeplyFlattenedArray);

// Expected output:
// [1, 2, 3, 4, 5]

In this second example, deeplyNestedArray.flat(4) flattens the array to 4 levels deep, resulting in a completely flattened array.

Live Playground, Try it Yourself

Using the flat method can simplify your code when you're working with nested arrays in JavaScript.