110_getAllButLastElement.js

/*
Write a function called "getAllButLastElementOfProperty".

Given an object and a key, "getAllButLastElementOfProperty" returns an array containing all but the last element of the array located at the given key.

Notes:
* If the array is empty, it should return an empty array.
* If the property at the given key is not an array, it return an empty array.
* If there is no property at the key, it should return an empty array. 

var obj = {
  key: [1, 2, 3]
};
var output = getAllButLastElementOfProperty(obj, 'key');
console.log(output); // --> [1,2]
*/

function getAllButLastElementOfProperty(obj, key) {
  var arr = obj[key];
  var allElementsButLast = [];
  if (!Object.keys(obj).includes(key) || arr.length === 0 || !Array.isArray(arr)) {
    return []
  } else {
    for (var i = 0; i < arr.length - 1; i++) {
      allElementsButLast.push(arr[i]);
    }
  }
  return allElementsButLast;
}