I just noticed that there is no prototype property on strings in JavaScript.
This is a pedagogical question while I try to wrap my head around the JavaScript type system but what gives?
How come "abc".toString() works? And how would I go about extending strings? If I wanted to be able to do "hey you!".alertDialog() for example?
String.prototype.alertDialog = function() { alert(this); }; String.prototype is the string prototype.
A word of warning when messing with prototype and Object data types, if you use a for loop, the full function will come back as one of the key/value pairs. See the basic examples below and comments.
// Basic hash-like Object var test = { 'a':1, 'b':2, 'c':3, 'd':4 }; // Incorrect // badAlerter prototype for Objects // The last two alerts should show the custom Object prototypes Object.prototype.badAlerter = function() { alert('Starting badAlerter'); for (var k in this) { alert(k +' = '+ this[k]); } }; // Correct // goodAlerter prototype for Objects // This will skip functions stuffed into the Object. Object.prototype.goodAlerter = function() { alert('Starting goodAlerter'); for (var k in this) { if (typeof this[k] == 'function') continue; alert(k +' = '+ this[k]) } }; test.badAlerter(); test.goodAlerter(); 
String? And you should not use a for in with Arrays either. However, for maximum compatibility, it's best not to modify the prototype of native JS object