/* Finds the lowest common multiple of two numbers */
function LcmCalculator(x, y) { // constructor function
var checkInt = function (x) { // inner function
if (x % 1 !== 0) {
throw new TypeError(x + "is not an integer"); // throw an exception
}
return x;
};
this.a = checkInt(x)
// ^ semicolons are optional
this.b = checkInt(y);
}
// The prototype of object instances created by a constructor is
// that constructor's "prototype" property.
LCMCalculator.prototype = { // object literal
constructor: LCMCalculator, // when reassigning a prototype, set the constructor property appropriately
gcd: function () { // method that calculates the greatest common divisor
// Euclidean algorithm:
var a = Math.abs(this.a), b = Math.abs(this.b), t;
if (a < b) {
// swap variables
t = b;
b = a;
a = t;
}
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 itself,
// so that this.gcd refers to this "redefinition" instead of LCMCalculator.prototype.gcd.)
// Also, 'gcd' == "gcd", this['gcd'] == this.gcd
this['gcd'] = function() {
return a;
};
return a;
},
"lcm"/* can use strings here */: function() {
// Variable names don't collide with object properties, e.g. |lcm| is not |this.lcm|.
// not using |this.a * this.b| to avoid FP precision issues
var lcm = this.a / this.gcd() * this.b;
// Only need to calculate lcm once, so "redefine" this method.
this.lcm = function() {
return lcm;
};
return lcm;
},
toString: function () {
return "LCMCalculator: a = " + this.a + ", b = " + this.b;
}
};
// Note: Array's map() and forEach() are defined in JavaScript 1.6.
// They are are implemented in Firefox, Chrome, Opera etc. but currently not in Internet Explorer.
// They are used here to demonstrate JavaScript's inherent functional nature.
[[25, 55],[21, 56],[22, 58],[28, 56]].map(function(pair) { // array literal + mapping function
return new LCMCalculator(pair[0], pair[1]);
}).sort(function(a, b) { // sort with this comparative function
return a.lcm() - b.lcm();
}).forEach(function(obj) {
/* Note: print() is a JS builtin function available in Mozilla's js CLI;
* It is functionally equivalent to Java's System.out.println().
* Within a web browser, print() is a very different function
* (opens the "Print Page" dialog),
* so use something like document.write() or alert() instead.
*/
// print (obj + ", gcd = " + obj.gcd() + ", lcm = " + obj.lcm());
// alert (obj + ", gcd = " + obj.gcd() + ", lcm = " + obj.lcm());
document.write(obj + ", gcd = " + obj.gcd() + ", lcm = " + obj.lcm() + "<br>");
});
//Wikipedia's advanced example on wikipedia's page on javascript
