27.3.1: JavaScript Examples
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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:
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//
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.
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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:
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+, -, *, /, 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:
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function input(text)
defines a function that checks the JavaScript environment and reads from the console, the current document, or standard input as appropriate.