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callbacks.js
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82 lines (65 loc) · 2.24 KB
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// Create a callback function and invoke the 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:
function firstItem(arr, cb) {
return cb(arr[0]);
}
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, console.log) // 4
function last(arr, cb) {
// last passes the last item of the array into the callback.
cb(arr[arr.length - 1]);
}
// last(items, console.log) // Gum
function sumNums(x, y, cb) {
// sumNums adds two numbers (x, y) and passes the result to the callback.
cb(x + y);
}
// sumNums(5, 10, console.log) // 15
// sumNums(-10, -10, console.log) // -20
function multiplyNums(x, y, cb) {
// multiplyNums multiplies two numbers and passes the result to the callback.
cb(x * y);
}
// multiplyNums(0, 10, console.log) // 0
// multiplyNums(0, -100, console.log) // 0
// multiplyNums(6, 10, console.log) // 60
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)){
cb(true)
} else {
cb(false)
}
}
// contains('Pencil', items, console.log) // true
// contains('Milk', items, console.log) // false
// contains({'supply': 'chalk'}, items, console.log) // false
/* STRETCH PROBLEM */
const list = ["Lebron", "Steph", "Russell", "Steph", "LeBron"]
function removeDuplicates(array, cb) {
// removeDuplicates removes all duplicate values from the given array.
let deduped = [];
array.forEach(function(element){
if(deduped.includes(element) === false) {
deduped.push(element);
}
});
cb(deduped)
// Pass the duplicate free array to the callback function.
// Do not mutate the original array.
}
removeDuplicates(list, console.log)