ES10 subtotal flat and flatmap

1.flat()

Flattening arrays , Or array dimensionality reduction !

adopt

let arr = [1,[2,3],5,[4,[6,7]]];

let arr2 = arr.flat(); // Reduce the dimension of the array to [1,2,3,5,4[6,7]]

Simply put, the array in the array is disassembled and inserted into the current position

flat() It can take parameters, and the default is 1 in other words

let arr2 = arr.flat(); The equivalent is let arr2 = arr.flat(1);

The function of the parameter is to identify the multidimensional array of reduced dimensions as 2 The third level subarray contained in the time array [6,7] It will also be resolved as [1, 2, 3, 5, 4, 6, 7]

2.flatMap()

This method and flat It will also reduce the dimension of the array However, this method will only reduce the dimension once And the elements in the array can be iterated through return return ( It doesn't change the original array You need to use a variable container to accept )

let arr = [1,[2,3],5,[4,[6,7]]];

let arr2 = arr.flatMap(item => {

  // It can be calculated here

  // return The number will generate a new array

  return item

}); // Reduce the dimension of the array to [1,2,3,5,4[6,7]]
console.log(arr2, arr)
// [1, 2, 3, 5, 4, Array(2)]   [1,[2,3],5,[4,[6,7]]]