/** Averages the first and last value of an array. Return null if the array has fewer than 2 elements.
* @param {number[]} arr - The input array
* @returns {number} - The average of the first and last values
*/
function firstAndLastAverage() {
}
/** Duplicates all values inside an array.
* Sample input: [1,4,2,5]
* Sample output: [1,4,2,5,1,4,2,5]
* @param {number[]} arr - The input array
* @returns {number[]} - The duplicated array
*/
function duplicateArray() {
}
/** Removes the first 3 elements from an array. If the array has fewer than 3 elements, return an empty array.
* @param {any[]} arr - The input array
* @returns {any[]} - The array with the first 3 elements removed
*/
function removeFirstThreeElements() {
}
module.exports = {
firstAndLastAverage,
duplicateArray,
removeFirstThreeElements
}