lib/rotjs-library/manual/pages/js.html

<h2>JavaScript prototype improvements</h2>

<p><strong>rot.js</strong> adds several new methods to JavaScript primordial objects: <code>Array</code>, <code>String</code>, <code>Number</code>, <code>Date</code>, <code>Object</code> and <code>Function</code>. Some of these are <a href="http://en.wikipedia.org/wiki/ECMAScript#ECMAScript.2C_5th_Edition">ECMAScript 5</a> 
<a href="http://en.wikipedia.org/wiki/Polyfill">polyfills</a>, some are purely syntactic sugar.</p>

<h3>Array</h3>

<div class="example">
SHOW(
	["apples", "oranges", "zombies"].random(),
	["apples", "oranges", "zombies"].randomize()
);</div>

<h3>String</h3>

<p>A more verbose explanation about how <code>String.format</code> works is available on a dedicated <a href="#format">string formatting page</a>.

<div class="example">
SHOW(
	"hello world".capitalize(),
	"hello %s, this is %s".format("world", "sparta"),
	"7".lpad("0", 3),
	"123".rpad(".", 6)
);</div>

<h3>Number</h3>

<p>The built-in modulus operator (%) yields negative results for negative arguments. <code>Number.prototype.mod</code> is guaranteed to return a positive value.</p>

<div class="example">
SHOW(
	( 15)  %  7 ,
	(-15)  %  7 ,
	( 15).mod(7),
	(-15).mod(7)
);</div>

<h3>Object</h3>

<p><code>Object.create</code> is a standardized way to create a new object with a hidden prototype link to other given object.</p>

<div class="example">
var obj1 = {price: 100};
var obj2 = Object.create(obj1);

SHOW(obj2.price);</div>

<h3>Date</h3>

<div class="example">SHOW(Date.now()); /* same as new Date().getTime() */</div>

<h3>Function</h3>

<div class="example">
var F1 = function() {};
F1.prototype.alert = function() { SHOW("hi"); }

var F2 = function() {};
F2.extend(F1);

new F2().alert();</div>