01.js

'use strict'

// This is a comment

/*
   This is a comment
   on multiple lines
*/

// VARIABLES
//
// A variable is a symbol that represents a quantity that may vary.
//
// $identifier = value;

var age = 25   // The value 25 is assigned to variable age



// BASIC DATA TYPES

var temperature = -3.82                  // Number
var name = 'Nacho López'                 // String
var has_car = true                       // Boolean (only two values: true or false)



// ARITHMETIC OPERATIONS WITH NUMBERS
var x = 5
var y = 2

var z = x + y    // Addition.                                     Result: 7.
z = x - y        // Subtraction.                                  Result: 3.
z = x * y        // Multiplication.                               Result: 10.
z = x / y        // Division.                                     Result: 2.5.
z = x % y        // Modulo (remainder of the integer division).   Result: 1.

z++              // Increase the value of z by 1.                 Result: 2.
z--              // Decrease the value of z by 1.                 Result: 1.

z = 50 - x * 6 / -0.5         //
z = (50 - x) * 6 / -0.5       // The order of operations is as in mathematics
z = (50 - x * 6) / -0.5       //

z = 2 * z + 3                 // Remember: the symbol = assigns a value to the variable



// BASIC OPERATIONS WITH STRINGS
var a = 'GNU/'
var b = 'Linux'
var c = a + b           // Concatenation                          Result: 'GNU/Linux'.
c = a.repeat(3)         // Repetition                             Result: 'GNU/GNU/GNU/'.



// PRINT VARIABLES ON CONSOLE

console.log('Hello, world!')            // Prints on console: Hello, world!
console.log(x)                          // Prints the variable x

// You can print on console strings and variables
console.log('I have bought', x, 'oranges and', y, 'lemons.')



// DATA TYPE CONVERSION

var height = '95.4'
console.log(typeof(height))                 // Prints the current data type
height = Number(height)                     // Convert a string to number
console.log(typeof(height))

var altitude = -544.432
console.log(typeof(altitude))
altitude = String(altitude)                 // Convert a number to string
console.log(typeof(altitude))