js39.js

//Data Structures examples


/*In this reading, you'll learn about some of the most common examples of data structures.

The focus will be on working with the Object, Array, Map and Set data structures in JavaScript, through a series of examples.

Note that this reading will not include a discussion of some data structures that exist in some other languages, such as Queues or Linked Lists.  Although these data structures (and other data structures too!) can be custom-coded in JavaScript, the advanced nature of these topics and the difficulty with implementing related exercises means they are beyond the scope of this reading. 

Working with arrays in JavaScript

Previously, you've covered a lot of concepts related to how to work with JavaScript arrays.

However, there are still a few important topics that can be covered, and one of those is, for example, working with some built-in methods.

In this reading, the focus is on three specific methods that exist on arrays:

    5.forEach 
    4.filter
    3.map
*/


//The forEach() method
//Arrays in JavaScript come with a handy method that allows you to loop over each of their members. 
const fruits = ['kiwi','mango','apple','pear'];
function appendIndex(fruit, index) {
    console.log(`${index}. ${fruit}`)
}
fruits.forEach(appendIndex);
//To explain the syntax, the forEach() method accepts a function that will work on each array item. That function's first parameter is the current array item itself, and the second (optional) parameter is the index.


//The filter() method
//Another very useful method on the array is the filter() method. It filters your arrays based on a specific test. Those array items that pass the test are returned.
const nums = [0,10,20,30,40,50];
nums.filter( function(num) {
    return num > 20;
})


//The map method
//Finally, there's a very useful map method. 
//This method is used to map each array item over to another array's item, based on whatever work is performed inside the function that is passed-in to the map as a parameter. 
[0,10,20,30,40,50].map( function(num) {
    return num / 10
})


//Working with Objects in JavaScript
//A lot of the information on how to work with objects in JavaScript has already been covered in this course.
//The example below demonstrates how to use the object data structure to complete a specific task. This task is to convert an object to an array:
const result = [];
const drone = {
    speed: 100,
    color: 'yellow'
}
const droneKeys = Object.keys(drone);
droneKeys.forEach( function(key) {
    result.push(key, drone[key])
})
console.log(result)