As well as the Global object there are several other pre-defined types in core JavaScript with useful properties and methods.
Array
a.length, a.sort(), a.push(), a.pop(), a.reverse(), etc
Date
var now = new Date ();
d.getDay (); // etc
d.getMilliseconds (); // for differencing
var then = new Date (millisecs); // Since 1970.0
d.toLocaleString (); // Taking time zone into account, from your system
Math
Math.PI, Math.abs (), Math.sqrt (), Math.sin (), etc
Number
n.toString (), n.toPrecision (2), etc
Object
o.toString (), o.valueOf ()
RegExp
new RegExp (pattern, attributes)
// Regular Expression - there is a page about, soon
String
s.length // a property, not a method (unlike in Java)
var s = "Some text.";
var a = s.charAt (3); // "e"
var b = s.charCodeAt (4); // 32
var c = s.concat (" ", "Some more text.");
// To concatenate any number of strings
var d = String.fromCharCode (65); // "A".
// NB: static function, requires type name
var e = s.indexOf ("text"); // 5
var f = s.indexOf ("TEXT"); // -1, meaning not found
var g = c.indexOf ("text", 6);
// Starting at index 6 - find the 2nd one
var h = c.lastIndexOf ("text"); // Finds the 2nd one
var j = s.substr (5, 4); // "text": 4 chars at index 5
var k = s.substring (5, 9); // "text": chars from 5 to before 9
var m = s.toLowerCase (); // or s.toUpperCase ()
var n = s.split (" ");
// Returns array of substrings, split on the separator character