• Your task is below the lesson

Users interact with computers in many ways. Your keyboard, mouse or trackpad, microphone, touchscreen, and stylus are all different ways that we provide input to the computer. We click on things we see or use keys on the keyboard to control an object or enter text. We're going to start with entering text.

Many programming languages have a chunk of code built-in for listening to the keyboard. In Python the command is input(), in Java it's System.console().readLine(); but in JavaScript it's prompt().

We're not using browser JavaScript, we're using NodeJS. So we need to install the prompt code. You only have to do this once on your computer.

In a terminal, make sure you have npm installed by running:

sudo apt update
sudo apt install npm

Install the prompt-sync code library by running:

npm install prompt-sync

Now you're ready to use prompt() in your code!

We have to tell NodeJS that we want to use the prompt-sync library in our code. For this, we will add the following to the top of our code file - it declares the prompt() command:

const prompt = require('prompt-sync')();

After preparing the code, we can ask the user to enter something and store it in a variable.
Here are a few examples:

/* main.js */
const prompt = require('prompt-sync')();

let age = prompt("How old are you? ");
console.log("You said you are", age, "years old.");

let name = prompt("What is your name? ");
age = prompt("How old is your dog? ");

Even the age variable in the example above will be considered a word, no matter if the user enters a number. This causes a problem with math.

Try this in your own console:

let age = prompt("How old are you? ");
console.log(age + 5);  // What do you think will print?

We can (try to) convert a String to a number:

// We have a few options
let my_value = Math.PI;
my_value = parseInt(my_value);   // 3
my_value = parseInt("year2022"); // NaN
my_value = parseInt("2022year"); // 2022

my_value = parseFloat("3.14");   // 3.14
my_value = parseFloat("56");     // 56

my_value = Number("year2022");   // NaN
my_value = Number("2022year");   // NaN
my_value = Number("3.14");       // 3.14

Examples:

let age = parseInt("twelve");
console.log(age);   // NaN

let year = parseInt("2022.5");
console.log(year);  // 2022

We can get the length of a String:

let name = "Mr. Squirrel";
console.log(name.length)            // 12

"St. Matthew High School".length;   // 23
let my_string = " spa ce!".length;  //  8

Time to try the task.

🐿️

• The lesson is above

Create a new code file called "1.4 - User Input.js" and work within that file.

• Add the required declaration for prompt-sync (see the lesson above)

• Print "1.4 - User Input" to the console.

• Use the prompt() function to ask the user for the year they were born:
  

What year were you born? >

• Print: "You entered " and then the number they entered, on one line.
  

You entered 1980

• Then print "You are likely <age> years old"

You entered 2008
You are likely 15 years old

• Ask the user for their name.
• Print out "Hi, <name>. You were born in <year> and you are likely <age> years old."

What is your name? > Sara
Hi, Sara. You were born in 2008 and you are likely 15 years old.

• Print "Your name is <x> letters long." (where <x> is the length of their name.)

Your name is 4 letters long.

• Ask for a temperature in Farenheit and convert it to Celsius (remember, we did this in the previous lesson)

What else can you think of doing with the prompt function?