Daily Codewars #27

Question

codewars link (opens new window) Create the function prefill that returns an array of n elements that all have the same value v. See if you can do this without using a loop.

You have to validate input:

v can be anything (primitive or otherwise) if v is ommited, fill the array with undefined if n is 0, return an empty array if n is anything other than an integer or integer-formatted string (e.g. '123') that is >=0, throw a TypeError When throwing a TypeError, the message should be n is invalid, where you replace n for the actual value passed to the function.

Code Examples

prefill(3,1) --> [1,1,1]

prefill(2,"abc") --> ['abc','abc']

prefill("1", 1) --> [1]

prefill(3, prefill(2,'2d'))
  --> [['2d','2d'],['2d','2d'],['2d','2d']]

prefill("xyz", 1)
  --> throws TypeError with message "xyz is invalid"

1번째 인자만큼 2번째 인자로 배열을 채우는 문제이다.

My Solution

function prefill(n, v) {
  try {
    var arr = Array.apply(null, Array(typeof n=='boolean'? parseInt(n): +n));
    return arr.map(function() {
      return v;
    });
  } catch (e) {
    throw new TypeError(n+' is invalid');
  }
}

try catch문을 직접 써본건 처음이다! Array.apply(null, Array(5))와 같이 배열을 초기화한다. 그냥 new Array(3)하면 length는 3이지만 생긴건 []인 배열이 나오니까. 그리고 맵 돌려줬다.

@abhiaiyer91's Solution

function prefill(num, value) {
  if(typeof num === 'boolean' || ~~num != num || +num < 0) throw new TypeError(num + ' is invalid')
  return Array.apply(null, Array(+num)).map(function (d,i) { return value })
}

같은 방식으로 map을 돌려주되, 앞에 boolean, float등을 처리하는 if를 넣어주었다 . 그냥 throw를 던지면 되는구나.

@handyCAPS's Solution

function prefill(n, v) {
  if (/\D/g.test(n) || n < 0) {throw new TypeError(n + ' is invalid')}
  return Array.apply(null, new Array(parseInt(n, 10))).map(function() {return v;});
}

이사람은 정규표현식으로 처리!