recursion 递归

function rangeOfNumbers(startNum, endNum) {//1 5
  if(startNum == endNum){
    return [endNum];//第一次return，不执行else
  }else {
    var array = rangeOfNumbers(startNum, endNum-1);
	//var array = [1, 2, 3, 4]
    array.push(endNum);
	//[1, 2, 3, 4].push(5);
    return array;
	//return [1, 2, 3, 4, 5];
  }
};

https://www.freecodecamp.org/learn/javascript-algorithms-and-data-structures/basic-javascript/use-recursion-to-create-a-range-of-numbers