JS Array flattening

// flattening a simple two-dimensional array  = [One, [], [+], [], [] , [ "One", " "], "" "," "", "" "," "

The main use of the Join method:

// if the element in the array is an array, the array inside will also call the join ()  = [[1,2],3//  1,2-3

Method 2:

// flattening a simple two-dimensional array  = [One, [], [+], [], [] , [ "One", " "], "" "," "", "" "," "

Knowledge Points:

// 1,2,c // The string returned by calling the join () method with no arguments is the same as above. 

Method 3:

flat()The default is to "flatten" only one layer, and if you want to "flatten" multiple layers of nested arrays, you can flat() write the parameter of the method as an integer representing the number of layers you want to flatten, which defaults to 1.

[1, 2, [3, [4, 5]]].flat () // [1, 2, 3, [4, 5]] [1, 2, [3, [4, 5]]].flat (2)//  [1, 2, 3, 4, 5]

If you want to turn into a one-dimensional array regardless of how many layers are nested, you can use Infinity keywords as arguments.

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

JS Array flattening