callbacks.js

// Create a higher order function and invoke the callback function to test your work. You have been provided an example of a problem and a solution to see how this works with our items array.  Study both the problem and the solution to figure out the rest of the problems.

const items = ["Pencil", "Notebook", "yo-yo", "Gum"];

/* 

  //Given this problem: 
  
  function firstItem(arr, cb) {
    // firstItem passes the first item of the given array to the callback function.
  }

  // Potential Solution:

  // Higher order function using "cb" as the call back
  function firstItem(arr, cb) {
    return cb(arr[0]);
  }

  // Function invocation 
  firstItem(items, function(first) {
    console.log(first)
  });

*/

function getLength(arr, cb) {
  // getLength passes the length of the array into the callback.
  cb(arr.length);
}
getLength(items, function(arrayItem) {
  console.log(arrayItem);
});

function last(arr, cb) {
  let lastItem = arr[arr.length - 1];
  cb(lastItem);
  // last passes the last item of the array into the callback.
}
last(items, cb => console.log(cb));

function sumNums(x, y, callback) {
  return callback(x + y);

  // sumNums adds two numbers (x, y) and passes the result to the callback.
}
sumNums(2, 4, function(chris) {
  console.log(chris);
});

function multiplyNums(x, y, callback) {
  return callback(x * y);

  // multiplyNums multiplies two numbers and passes the result to the callback.
}

multiplyNums(3, 5, function(raspberry) {
  console.log(raspberry);
});

function contains(item, list, callback) {
  for (let i = 0; i < list.length; i++) {
    if (item === list[i]) {
      return callback(true);
    } else {
      return callback(false);
    }
  }
}
contains("lollipop", items, function(raspberry) {
  console.log(raspberry);
});

/* STRETCH PROBLEM */

function removeDuplicates(array, cb) {
  // removeDuplicates removes all duplicate values from the given array.
  // Pass the duplicate free array to the callback function.
  // Do not mutate the original array.
}