public/subjects/DPxAI/listed

Listed

Mindful AI mode

Context

Sometimes we don't need a key, we just want a list of things, JS has a special type for that, called an array.

In JavaScript, arrays are essential tools for handling these lists efficiently.

Let's discover them together!

AI-Powered Learning Techniques

Example-Based Learning Technique: This type of prompt encourages the AI to provide concrete examples to illustrate concepts, making it easier to understand and apply them.

Find the examples across the subject ;)

Concepts

Understanding Arrays

Arrays are special types of objects in JavaScript used to store lists of items. Unlike objects, arrays don't have keys for each element, just a list of values.

Example of an Array

Let's see an example of an array:

let batteryLevels = [
  80, // <- no keys!
  60,
  90,
  50,
];

// or for brevity, we often write them on a single line like so:

let batteryLevels = [80, 60, 90, 50];

Indexes in Arrays

The position of an element in an array is called its index, starting from 0. So, our batteryLevels array is roughly equivalent to writing this object:

let batteryLevelsObject = {
  0: 80,
  1: 60,
  2: 90,
  3: 50,
};

Accessing Array Values

To access a value in an array, use the index inside square brackets:

let batteryLevels = [80, 60, 90, 50];
console.log(batteryLevels[0]); // -> 80
console.log(batteryLevels[3]); // -> 50
console.log(batteryLevels[6]); // -> undefined

Using the .length Property

Arrays keep track of how many elements they contain using the .length property:

console.log([].length); // -> 0
console.log([80].length); // -> 1
console.log([80, 60, 90, 50].length); // -> 4

Replacing an Array Value

You can replace an array value by accessing it via its index and assigning a new value:

let robotTasks = [
  "Charging",
  "Cleaning",
  "Maintenance",
  "Patrolling",
  "Greeting",
];

// Let's say I want to change 'Charging' to 'Upgrading'
robotTasks[0] = "Upgrading";

console.log(robotTasks);

Now, the array looks like this:

["Upgrading", "Cleaning", "Maintenance", "Patrolling", "Greeting"];

Prompt Example:

• "How does accessing an array element differ from accessing an object property?"

• "Can you think of a scenario where using an array to store values would be more beneficial than using separate variables?"

Instructions

Task 1:

You must declare a variable components that contains 4 strings, one for each robot component.

Task 2:

We provide you a variable robotParts that contains some elements. You will have to access them and assign their values to variables:

• A variable firstPart for the first element of the robotParts list
• A variable lastPart for the last element of the robotParts list
• A variable comboParts as an array of 2 elements, the last and the first element of the robotParts list, in that order. Example: if robotParts is [1, 2, 3]

-firstPart would be 1

-lastPart would be 3

-comboParts would be [3, 1]

Task 3:

You must replace the third element of the provided replaceComponents array with the string 'enhanced'.

Example:

let replaceComponents = ["motor", "sensor", "battery"];
// expect -> ['motor', 'sensor', 'enhanced']

You must swap the first and second element of the provided swapComponents array.

Example:

let swapComponents = ["motor", "sensor", "battery"];
// expect -> ['sensor', 'motor', 'battery'] (last element is untouched)

"Programming is like building a robot. You start with the basics, but the fun really begins when you start swapping parts and adding enhancements!"