Basic JavaScript - Use Recursion to Create a Countdown

JavaScript
1

Tell us what’s happening:
Why do we use unshift here?
Your code so far

// Only change code below this line
function countdown(n){
  if (n<1){
    return [];
}
else {
   countdownArr=countdown(n-1);
  countdownArr.unshift(n);
  return countdownArr;
}


}
console.log(countdown(10));
var countdownArr=[]
// Only change code above this line

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Challenge: Basic JavaScript - Use Recursion to Create a Countdown

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2

I believe i might have answered my own question. When running this code through a given number, I, for some reason envisioned it being a literal countdown, but it runs from one, with ‘n’ being the FINAL number. Hence, .unshift returns the last number first in the Arr.

3

now i got it. The arr executes first and then the unshift is executed. got it.

4

.unshift() appends value to the beginning of the array (unlike .push() which appends to the end). Remember that the recursion, as written here, runs through the entire sequence from n to 1 first before appending anything to your countdownArr. Because all n-1 has already been evaluated before the appending, the appending happens in reverse order of the evaluation. Thus, .unshift() produces an array in descending order.

5

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