Map and filter are useful methods for manipulating arrays. Map lets you create a new array by applying a function to each item in the original. Filter lets you create a new array with only elements that pass a certain condition.
You may have used the native JavaScript versions (e.g. array.map()), but we're going to be implementing our own today to see how they work. You're only allowed to use for loops for this challenge.
Click for a hint
You could use a normal for loop, or take a look at for...of loops.
You can open challenge/test.html in your browser to see some failing tests in the console. These should pass once you've completed parts one and two below.
Clone this repo, then open challenge/map-filter.js in your editor. Right now the map function just returns the array it is given. Instead you should make it return a new array, with each element transformed by calling the fn argument with the element.
Example usage:
map(x => x * 10, [1, 2, 3]);
// [10, 20, 30]In the same file edit the filter function so it returns a new array with only elements that pass the test provided by the fn argument.
Example usage:
filter(x => x > 1, [1, 2, 3]);
// [2, 3]
Open challenge/pokemon.html in your browser. You should see an input and a list of pokémon names. Open challenge/pokemon.js in your editor. The code is looping over an array of pokémon and rendering their names to the list on the page.
Unfortunately the data isn't great: there's an unnecessary "." character at the end of each name. Use your map function to create a new array where the names have the "." removed.
At the end of the file there's an event listener for the input. It's supposed to filter the list of pokémon based on what the user types. Use your filter function to make this work.
Click for a hint
You might want to read about string.includes().