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2.20: JavaScript Examples

  • Page ID
    10617
  • Overview

    The following examples demonstrate data types, arithmetic operations, and input in JavaScript.

    Data Types

    // This program demonstrates variables, literal constants, and data types.
    
    var n;
    var s;
    var b;
        
    n = 1.23456789012345;
    s = "string";
    b = true;
        
    output("Number n = " + n);
    output("String s = " + s);
    output("Boolean b = " + b);
    
    // Check the JavaScript environment and write to the console, 
    // the current document, or standard output as appropriate.
    // Reference: http://progopedia.com/example/hello-world/114/
    function output(text) {
      if (typeof console === 'object') {
        console.log(text);
      } 
      else if (typeof document === 'object') {
        document.write(text);
      } 
      else {
        print(text);
      }
    }
    

    Output

    Number n = 1.23456789012345
    String s = string
    Boolean b = true
    

    Discussion

    Each code element represents:

      • // begins a comment
      • var n, s, and b define variables
      • ; ends each line of JavaScript code
      • i = , d = , s =, b = assign literal values to the corresponding variables
      • output() calls the output function
      • function output(text) defines a output function that checks the JavaScript environment and writes to the console, the current document, or standard output as appropriate.

    Arithmetic

    // This program demonstrates arithmetic operations.
    
    var a;
    var b;
        
    a = 3;
    b = 2;
    output("a = " + a);
    output("b = " + b);
    output("a + b = " + (a + b));
    output("a - b = " + (a - b));
    output("a * b = " + a * b);
    output("a / b = " + a / b);
    output("a % b = " + (a % b));
    
    // Checks the JavaScript environment and writes to the console, 
    // the current document, or standard output as appropriate.
    // Reference: http://progopedia.com/example/hello-world/114/ 
    function output(text) {
      if (typeof console === 'object') {
        console.log(text);
      } 
      else if (typeof document === 'object') {
        document.write(text);
      } 
      else {
        print(text);
      }
    }
    

    Output

    a = 3
    b = 2
    a + b = 5
    a - b = 1
    a * b = 6
    a / b = 1.5
    a % b = 1
    

    Discussion

    Each new code element represents:

    • +, -, *, /, and % represent addition, subtraction, multiplication, division, and modulus, respectively.

    Temperature

    // This program converts an input Fahrenheit temperature to Celsius.
    
    var fahrenheit;
    var celsius;
        
    output("Enter Fahrenheit temperature:");
    fahrenheit = input();
    
    celsius = (fahrenheit - 32) * 5 / 9;
    
    output(fahrenheit.toString() + "° Fahrenheit is " + celsius + "° Celsius");
    
    // Checks the JavaScript environment and reads from the console, 
    // the current document, or standard input as appropriate.
    function input(text) {
      if (typeof console === 'object') {
        return prompt(text)
      }
      else {
        output(text);
        var isr = new java.io.InputStreamReader(java.lang.System.in); 
        var br = new java.io.BufferedReader(isr); 
        var line = br.readLine();
        return line.trim();
      }
    }
    
    // Checks the JavaScript environment and writes to the console, 
    // the current document, or standard output as appropriate.
    // Reference: http://progopedia.com/example/hello-world/114/ 
    function output(text) {
      if (typeof console === 'object') {
        console.log(text);
      } 
      else if (typeof document === 'object') {
        document.write(text);
      } 
      else {
        print(text);
      }
    }
    

    Output

    Enter Fahrenheit temperature:
     100
    100° Fahrenheit is 37.7777777777778° Celsius
    

    Discussion

    Each new code element represents:

    • function input(text) defines a function that checks the JavaScript environment and reads from the console, the current document, or standard input as appropriate.