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callbacks.js
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82 lines (59 loc) · 2.15 KB
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// 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) {
return cb = arr.length; // getLength passes the length of the array into the callback.
}
// invoke getLength()
console.log(getLength(items));
function last(arr, cb) {
return cb = (arr[arr.length-1]);// last passes the last item of the array into the callback.
}
// invoke last()
console.log(last(items));
function sumNums(x, y, cb) {
return cb = x + y;// sumNums adds two numbers (x, y) and passes the result to the callback.
}
// invoke sumNums()
console.log(sumNums(4, 6));
function multiplyNums(x, y, cb) {
return cb = x * y;// multiplyNums multiplies two numbers and passes the result to the callback.
}
// invoke multiplyNums
console.log(multiplyNums(2,8));
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.
for (let i=0; i<items.length; i++) {
if (list[i] === item) {
return cb = true;
}
else {
return false;
}
}
return cb;
}
// invoke contains()
console.log(contains('Pencil', items));
console.log(contains('Sharpie', items));
/* 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.
}