Working with arrays is an essential part of being a javascript developer. A lot of the time js developers have an array of some objects. That could be users, products, posts, cars etc. Working with these arrays, js developers so often need to filter the arrays, change the structure of the array, sort them or loop through them.

Say you would like to write a program that doubles the odd numbers in an array and throws away the even number.

rewrite the above program using `map` and `filter` don't forget to use `=>`

Copy the movies array in the movies.js file. Use this array to do the following tasks:

1. Create a new array that has an extra key called tag. The tag is based in the rating: Good (>= 7), Average (>= 4 and < 7), Bad (< 4).

1. Using chaining, first map the movies array to only the rating of the movies. Now filter the movies array to only contain the movies rated higher than 6. Try do it where you define the functions as constants you provide to the filter and map functions.

1. Count he number of movies containing the following keywords: `["The", "dog", "who", "is", "not", "a", "man"]`. Can you make sure the search is case insensitive?

1. Calculate the average rating of all the movies using reduce. *Optional*

1. Count the total number of Good, Average and Bad movies using reduce. *Optional*

We have been hired for a company to do a SPA - Single Page App for them. It is a website where a user can add products to the users shopping cart. The products can be filtered and sorted based on what products the user wants to see.

In the homework folder there is a project you should continue working on. So Copy the files into your hyf-homework week 6 folder and start working in the main.js file.

There is a function available to you called `getAvailableProducts`. Calling this function will return an array of products. There can be from 0 - 30 products in the array. The products are represented by objects that has the following keys: `id`, `name`, `price`, `rating`, `shipsTo`.

Call `getAvailableProducts` function to get the products array. Now add these products (as li elements) to the `ul` under the section with the classname products. Here is an example of how the individual li element should look:

In order for analysing the product prices we need to send the prices of the products to a server.

A user can filter the search result in different ways. One way is by choosing to only see products that ship from a certain country. This can be helpful for the user, so the user does not spend to much time looking for products that can not be shipped to the user. We need to create that functionality: When the user selects a country, the products should be updated with the products that ship to that country.

No matter how small or how big. Create some feature.

When clicking the Add to cart button for a product, that product should be added to the `ul` found under the section with the classname cart. The product should be added as a an `li` item. Like this:

</li>;

2. When adding the li tags to the ul. You can for every product in the products array create a new li element using `document.createElement('li')`. You then set the innerHTML as is specified above and then attach a clickListner: `createdLiElement.addEventListener('click', () => {});` The callback function has access to the product object because of something called `closures`. This approach i would say is the best way.

Hint 2: Have an array with the products in the shopping cart. Render the shopping cart using this array.

Calculate the total price of all the elements in the shopping cart. Investigate the array function called `reduce`. It reduces an array down to one value. Which is exactly what we want. To reduce the products in the shopping cart array down to a single value that is the total price.

The filter function works on arrays and it filters out elements in our array.

It takes a function as input. This function is called on every element in the array. Just like forEach. If this function we create returns true the element is saved in the, if we return false the element is filtered out.

The map function works on arrays. It maps (think transform) the elements of an array. Or from MDN: "The map() method creates a new array with the results of calling a provided function on every element in the calling array."

const carColors = cars.map(function(car) {

return car.color;

});

console.log(carColors); // ['lightYellow', 'lightBlue', 'lightCyan']

const carSpeeds = cars.map(function(car) {

return car.speed;

});

console.log(carSpeeds); // [45, 87, 78]