Flatten array.Flat (infinity)

 Flattening arrays 

 flat Used to flatten multidimensional arrays （ flat ）, Does not affect the original array , Return a new array .

[1, 2, [3, [4]]].flat() // [1, 2, 3, [4]]
1
   There is only one parameter depth, Used to specify the flattening depth , The default value is 1. if depth Specify as non positive number , Will return the original array , Designated as Infinity, No matter how many layers are flattened into a one-dimensional array .

[1, 2, [3, [4]]].flat(2) // [1, 2, 3, 4]
[1, 2, [3, [4]]].flat(0) // [1, 2, [3, [4]]]
[1, 2, [3, [4]]].flat(Infinity) // [1, 2, 3, 4]