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callbacks.js
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88 lines (67 loc) · 2.23 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) {
// getLength passes the length of the array into the callback.
return cb(arr.length)
}
getLength(items, function(length){
console.log(length);
})
function last(arr, cb) {
// last passes the last item of the array into the callback.
return cb(arr[arr.length - 1])
}
last(items, function(item){
console.log(item)
})
function sumNums(x, y, cb) {
// sumNums adds two numbers (x, y) and passes the result to the callback.
return cb(x + y)
}
sumNums(1, 2, function(item){
console.log(item)
})
function multiplyNums(x, y, cb) {
// multiplyNums multiplies two numbers and passes the result to the callback.
return cb(x * y)
}
sumNums(2, 2, function(item){
console.log(item)
})
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.
// return list.indexOf(item) > -1 ? cb(true) : cb(false)
return cb(list.includes(item))
}
contains('Penil', items, function(item){
console.log(item)
})
/* 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.
// array.forEach(item => duplicateFree.indexOf(item) =! duplicateFree.push(item))
return cb(array.filter((value, index, arr) => arr.indexOf(value) === index))
}
removeDuplicates([1, 1, 2, 3, 4, 4, 4, 6, 6], function(item){
console.log(item);
});