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callbacks.js
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80 lines (64 loc) · 2.11 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)
});
*/
// callback function
const log = console.log;
function getLength(arr, cb) {
// getLength passes the length of the array into the callback.
return cb(arr.length);
}
getLength(items, log);
function last(arr, cb) {
// last passes the last item of the array into the callback.
return cb(arr[arr.length - 1]);
}
last(items, log);
function sumNums(x, y, cb) {
// sumNums adds two numbers (x, y) and passes the result to the callback.
let z = x + y;
return cb(z);
}
sumNums(2, 4, log);
function multiplyNums(x, y, cb) {
// multiplyNums multiplies two numbers and passes the result to the callback.
let z = x * y;
return cb(z);
}
multiplyNums(2, 3, log);
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.
if (list.includes(item)) {
return cb(true);
} else {
return cb(false);
}
}
contains("Gum", items, log);
contains("Xerox", items, log);
/* STRETCH PROBLEM */
const nonUniqueValues = ["2", "2", "1", 1, 1, 2, "3", 3, "3", 4, 4, 4, "4"];
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 unique = array.filter((v, i, a) => a.indexOf(v) === i);
return cb(unique);
}
removeDuplicates(nonUniqueValues, log);