nonMutatingSplice.js

// *** Functional Programming: Remove Elements from an Array Using slice Instead of splice ***

// A common pattern while working with arrays is when you want to remove items and keep the rest 
// of the array. JavaScript offers the splice method for this, which takes arguments for the 
// index of where to start removing items, then the number of items to remove. If the second 
// argument is not provided, the default is to remove items through the end. However, the splice 
// method mutates the original array it is called on. 

// Here's an example:
//   var cities = ["Chicago", "Delhi", "Islamabad", "London", "Berlin"];
//   cities.splice(3, 1); // Returns "London" and deletes it from the cities array
//    cities is now ["Chicago", "Delhi", "Islamabad", "Berlin"]

// As we saw in the last challenge, the slice method does not mutate the original array, but
//  returns a new one which can be saved into a variable. Recall that the slice method takes 
//  two arguments for the indices to begin and end the slice (the end is non-inclusive), and 
//  returns those items in a new array. Using the slice method instead of splice helps to 
//  avoid any array-mutating side effects.

// Rewrite the function nonMutatingSplice by using slice instead of splice. It should limit 
// the provided cities array to a length of 3, and return a new array with only the first three items.
// Do not mutate the original array provided to the function.


function nonMutatingSplice(cities) {
  // Add your code below this line
  return cities.slice(0,3);
  
  // Add your code above this line
}
var inputCities = ["Chicago", "Delhi", "Islamabad", "London", "Berlin"];
nonMutatingSplice(inputCities);