Question

// 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.

}

// SOLUTION:

function firstItem(arr, cb) {

return cb(arr[0]);

}

// NOTES ON THE SOLUTION:

// firstItem is a higher order function.

// It expects a callback (referred to as `cb`) as its second argument.

// To test our solution, we can use the given `items` array and a variety of callbacks.

// Note how callbacks can be declared separately, or inlined.

// TEST 1 (inlined callback):

const test1 = firstItem(items, item => `I love my ${item}!`);

console.log(test1); // "I love my Pencil!"

// TEST 2 (declaring callback before hand):

function logExorbitantPrice(article) {

return `this ${article} is worth a million dollars!`;

};

const test2 = firstItem(items, logExorbitantPrice);

console.log(test2); // "this Pencil is worth a million dollars!"

*/

function getLength(arr, cb) {

// getLength passes the length of the array into the callback.

}

arr = [1, 12, 3, 2, 1, 5, 3, 4, 20]; //Sample array is taken

function print(array) {

array.forEach(function(eachName, index) {

console.log(index + 1 + ". " + eachName);

});

}

function last(arr, cb) {

// last passes the last item of the array into the callback.

}

function sumNums(x, y, cb) {

// sumNums adds two numbers (x, y) and passes the result to the callback.

}

function multiplyNums(x, y, cb) {

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

}

function contains(item, list, cb) {

// contains checks if an item is present inside of the given array/list.

// Pass true to the callback if it is, otherwise pass false.

}

/* 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.

}

Answer 1

If you have any doubts, please give me comment...

// 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.

// }

// SOLUTION:

function firstItem(arr, cb) {

return cb(arr[0]);

}

// NOTES ON THE SOLUTION:

// firstItem is a higher order function.

// It expects a callback (referred to as `cb`) as its second argument.

// To test our solution, we can use the given `items` array and a variety of callbacks.

// Note how callbacks can be declared separately, or inlined.

// TEST 1 (inlined callback):

const test1 = firstItem(items, item => `I love my ${item}!`);

console.log(test1); // "I love my Pencil!"

// TEST 2 (declaring callback before hand):

function logExorbitantPrice(article) {

return `this ${article} is worth a million dollars!`;

};

const test2 = firstItem(items, logExorbitantPrice);

console.log(test2); // "this Pencil is worth a million dollars!"

function getLength(arr, cb) {

// getLength passes the length of the array into the callback.

return cb(arr.length);

}

arr = [1, 12, 3, 2, 1, 5, 3, 4, 20]; //Sample array is taken

function print(array) {

array.forEach(function(eachName, index) {

console.log(index + 1 + ". " + eachName);

});

}

function last(arr, cb) {

// last passes the last item of the array into the callback.

return cb(arr[arr.length - 1]);

}

function sumNums(x, y, cb) {

// sumNums adds two numbers (x, y) and passes the result to the callback.

return cb(x + y);

}

function multiplyNums(x, y, cb) {

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

return cb(x * y);

}

function contains(item, list, cb) {

// contains checks if an item is present inside of the given array/list.

// Pass true to the callback if it is, otherwise pass false.

let result = false;

for (i = 0; i < list.length; i++) {

if (list[i] == item) {

result = true;

break;

}

}

return cb(result);

}

/* 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.

let result = [];

for (i = 0; i < array.length; i++) {

let exists = false;

for (j = 0; j < result.length; j++) {

if (array[i] == result[j])

exists = true;

}

if (!exists)

result.push(array[i]);

}

return cb(result);

}