Add Items to an Array with push() and unshift()

• An array's length, like the data types it can contain, is not fixed. Arrays can be defined with a length of any number of elements, and elements can be added or removed over time; in other words, arrays are mutable. In this challenge, we will look at two methods with which we can programmatically modify an array: Array.push() and Array.unshift().

• Both methods take one or more elements as parameters and add those elements to the array the method is being called on; the push() method adds elements to the end of an array

• The unshift() adds elements to the beginning. Consider the following:
  

function mixedNumbers(arr) {
let begArray = arr.unshift("I", 2, "three");
let endArray = arr.push(7, "VIII", 9);

  return arr;
}

console.log(mixedNumbers(['IV', 5, 'six'])); console will display 
["I", 2, "three", "IV", 5, "six", 7, "VIII", 9]

• Here We have defined a function, mixedNumbers, which we are passing an array as an argument. We modified the function by using push() and unshift() to add 'I', 2, 'three' to the beginning of the array and 7, 'VIII', 9 to the end so that the returned array contains representations of the numbers 1-9 in order.