mirror of
https://github.com/netsurf-browser/netsurf
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71 lines
2.7 KiB
JavaScript
71 lines
2.7 KiB
JavaScript
/* Finds the lowest common multiple (LCM) of two numbers */
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function LCMCalculator(x, y) { // constructor function
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var checkInt = function (x) { // inner function
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if (x % 1 !== 0) {
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throw new TypeError(x + " is not an integer"); // throw an exception
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}
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return x;
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};
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this.a = checkInt(x)
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// ^ semicolons are optional
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this.b = checkInt(y);
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}
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// The prototype of object instances created by a constructor is
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// that constructor's "prototype" property.
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LCMCalculator.prototype = { // object literal
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constructor: LCMCalculator, // when reassigning a prototype, set the constructor property appropriately
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gcd: function () { // method that calculates the greatest common divisor
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// Euclidean algorithm:
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var a = Math.abs(this.a), b = Math.abs(this.b), t;
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if (a < b) {
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// swap variables
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t = b;
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b = a;
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a = t;
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}
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while (b !== 0) {
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t = b;
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b = a % b;
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a = t;
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}
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// Only need to calculate GCD once, so "redefine" this method.
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// (Actually not redefinition—it's defined on the instance itself,
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// so that this.gcd refers to this "redefinition" instead of LCMCalculator.prototype.gcd.)
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// Also, 'gcd' === "gcd", this['gcd'] === this.gcd
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this['gcd'] = function () {
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return a;
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};
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return a;
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},
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// Object property names can be specified by strings delimited by double (") or single (') quotes.
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"lcm" : function () {
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// Variable names don't collide with object properties, e.g. |lcm| is not |this.lcm|.
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// not using |this.a * this.b| to avoid FP precision issues
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var lcm = this.a / this.gcd() * this.b;
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// Only need to calculate lcm once, so "redefine" this method.
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this.lcm = function () {
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return lcm;
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};
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return lcm;
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},
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toString: function () {
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return "LCMCalculator: a = " + this.a + ", b = " + this.b;
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}
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};
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//define generic output function; this implementation only works for web browsers
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function output(x) {
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document.body.appendChild(document.createTextNode(x));
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document.body.appendChild(document.createElement('br'));
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}
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// Note: Array's map() and forEach() are defined in JavaScript 1.6.
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// They are used here to demonstrate JavaScript's inherent functional nature.
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[[25, 55], [21, 56], [22, 58], [28, 56]].map(function (pair) { // array literal + mapping function
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return new LCMCalculator(pair[0], pair[1]);
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}).sort(function (a, b) { // sort with this comparative function
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return a.lcm() - b.lcm();
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}).forEach(function (obj) {
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output(obj + ", gcd = " + obj.gcd() + ", lcm = " + obj.lcm());
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});
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