Essentials of Javascript - Cultural View

JavaScript 5
Syntax and semantics
As of 2009, the latest version of the language is JavaScript 1.8.1. It is a superset of ECMAScript (ECMA-262)
Edition 3. Extensions to the language, including partial E4X (ECMA-357) support and experimental features
considered for inclusion into future ECMAScript editions, are documented here. [27]
Example - syntax and semantics
This sample code showcases various JavaScript features. The example can be executed with the following steps: (1)
Copy the code to a file with extension .htm. (2) Use the Mozilla or Firefox browser to open the file.
LCM Calculator
/* Finds the lowest common multiple of two numbers */
function LCMCalculator(x, y) { // constructor function
function checkInt(x) { // inner function
throwing
}
if (x % 1 != 0)
throw new TypeError(x + " is not an integer"); // exception
return x;
//semicolons are optional (but beware since this may cause
consecutive lines to be
}
//erroneously treated as a single statement)
this.a = checkInt(x)
this.b = checkInt(y)
// The prototype of object instances created by a constructor is
// that constructor's "prototype" property.
LCMCalculator.prototype = { // object literal
divisor
itself,
gcd : function() { // method that calculates the greatest common
// Euclidean algorithm:
var a = Math.abs(this.a), b = Math.abs(this.b), t;
if (a < b) {
}
t = b; b = a; a = t; // swap variables
while (b !== 0) {
}
t = b;
b = a % b;
a = t;
// Only need to calculate gcd once, so "redefine" this method.
// (Actually not redefinition - it's defined on the instance
// so that this.gcd refers to this "redefinition" instead of