Programming Fundamentals/Variable Examples JavaScript

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);
 
 function output(text) {
   if (typeof document === 'object') {
     document.write(text);
   } 
   else if (typeof console === 'object') {
     console.log(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 current document, the console, 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));
 
 function output(text) {
   if (typeof document === 'object') {
     document.write(text);
   } 
   else if (typeof console === 'object') {
     console.log(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");
 
 function input(text) {
   if (typeof window === 'object') {
     return prompt(text)
   }
   else if (typeof console === 'object') {
     const rls = require('readline-sync');
     var value = rls.question(text);
     return value;
   }
   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();
   }
 }
 
 function output(text) {
   if (typeof document === 'object') {
     document.write(text);
   } 
   else if (typeof console === 'object') {
     console.log(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 current window, the console, or standard input as appropriate.

References

• Wikiversity: Computer Programming

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