Recursively appending to an array with ternary operator not working

I’m trying to create a recursive function that returns an array of interger in a range of numbers.

If I use a ternary operator, the base case returns ‘undefined’. I can’t see where is the problem.

Using JSLint I get this message: "Wrap a ternary expression in parens, with a line break after the left paren."

The code:

function rangeOfNumbers(startNum, endNum) {
  return startNum === endNum
    ? startNum
    : rangeOfNumbers(startNum, endNum - 1).concat(endNum);
}

function rangeOfNumbers(startNum, endNum) {
  return startNum === endNum
    ? [startNum]
    : rangeOfNumbers(startNum, endNum - 1).concat(endNum);
}