The flat() method creates a new array by flattening a nested array up to the specified depth.
Example
flat() Syntax
The syntax of the flat() method is:
arr.flat(depth)
Here, arr is an array.
flat() Parameters
The flat() method takes a single parameter:
- depth - Integer specifying how deep a nested array should be flattened. Its default value is 1.
flat() Return Value
- Returns a flatted array with the sub-array elements concatenated into it.
Notes: The flat() method:
- does not change the original array.
- removes empty slots in arrays.
Example 1: Using flat() Method
Output
[ 1, 2, 3, 4, 5, 6, [ 7, 8 ] ]
In the above example, we have used the flat() method to flat the nested array numbers to depth 2.
numbers.flat(2) reduces the nesting of the numbers array and returns a flatted array with only one nesting i.e. [ 1, 2, 3, 4, 5, 6, [ 7, 8 ] ]
Example 2: flat() Without Default Depth Argument
Output
[ 1, 2, 3, 4, 5 ]
Here, we have not passed any depth argument in the flat() method.
The default depth argument is 1, so array1.flat() flattens array1 to depth 1.
Example 3: flat() to Remove Holes in Array
We can remove holes in an array that has empty slots using the flat() method. For example:
Output
[ 1, 3 ]
Recommended Reading: JavaScript Array flatMap()