Can anyone explain this Challenge solution?

Question

I will attach image of challenge solution that i cannot understand this solution not the challenge itself

Code :

function array(num,length){
  return [...Array(length).map((_,i) => num * (i+1)
}

Answer 1

First of all there are something wrong with the syntax: There is both a missing ] and ).

There is a function called "array" (maybe it is not the best name...). It takes two parameters: a number (num) and a length (length), both numbers.

length is used for defining and array (Array(length)). So length=4 will result in an array: [undefined,undefined,undefined,undefined]. map() is a function that takes an array and returns an array with a similar length. The array returned by map() contains numbers that are calulated based on the index (the i) and the parameter num, so first 0*3, then 1*3, then 2*3. The array is then returned as the "result" of calling the function "array".

Here I print out the array in the console:

function array(num, length){
  return [...Array(length)].map((_,i) => num * (i+1))
}

console.log(array(3, 4));