//we can add elements to middle of  array using splice

const strings=['a','b','c','d']

//go the 2nd index,remove 0 elements and then add 'alien' to it
strings.splice(2,0,'alien')

console.log(strings) //["a", "b", "alien", "c", "d"]

//what is the time complexity ???
//worst case is O(n). if we are adding to end of array then O(1)
//in our example we added to the middle of array so O(n/2)=>O(n)