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challenges.js
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/* ======================== CallBacks Practice ============================ */
const each = (elements, cb) => {
// Iterates over a list of elements, yielding each in turn to the `cb` function.
// This only needs to work with arrays.
for (let i = 0; i < elements.length; i++) {
cb(elements[i], i);
}
};
const map = (elements, cb) => {
// Produces a new array of values by mapping each value in list through a transformation function (iteratee).
// Return the new array.
const arr = [];
for (let i = 0; i < elements.length; i++) {
arr.push(cb(elements[i]));
}
return arr;
};
/* ======================== Closure Practice ============================ */
const limitFunctionCallCount = (cb, n) => {
// Should return a function that invokes `cb`.
// The returned function should only allow `cb` to be invoked `n` times.
let count = 0;
return (...args) => {
count++;
if (count <= n) return cb(...args);
return null;
};
};
const cacheFunction = cb => {
// Should return a funciton that invokes `cb`.
// A cache (object) should be kept in closure scope.
// The cache should keep track of all arguments have been used to invoke this function.
// If the returned function is invoked with arguments that it has already seen
// then it should return the cached result and not invoke `cb` again.
// `cb` should only ever be invoked once for a given set of arguments.
};
/* eslint-enable no-unused-vars */
/* ======================== Recursion Practice ============================ */
const reverseStr = str => {
// reverse str takes in a string and returns that string in reversed order
// The only difference between the way you've solved this before and now is that you need to do it recursivley!
};
const checkMatchingLeaves = obj => {
// return true if every property on `obj` is the same
// otherwise return false
};
const flatten = elements => {
// Flattens a nested array (the nesting can be to any depth).
// Example: flatten([1, [2], [3, [[4]]]]); => [1, 2, 3, 4];
};
module.exports = {
each,
map,
limitFunctionCallCount,
cacheFunction,
reverseStr,
checkMatchingLeaves,
flatten,
};