// generateID.js /* A couple of things here. * (1) Uses a self-executing function to eliminate all globals. * (2) Generates a static variable (genId.id) as a property of * a function object. * * Tested in IE7, FF2, Op9, and Sa3. * Some browsers treat double-clicks on the button as single clicks. * * HTML of the web page: * *

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You have not generated any IDs yet.

* * * ccv 2008-03-01 */ (function() // Anonymous self-executing function { var b = null; var p = null; // genId() // ------------------------------------------------------------ /* Returns the next value in a sequence on successive calls. */ function genId() { // Create static variable if it does not exist yet. if (!genId.id) genId.id = 0; return ++genId.id; } // handler() // ---------------------------------------------------------- /* Click hander for the button. Gets the next ID and displays * it. */ function handler(e) { var id = genId(); p.firstChild.nodeValue = "Your ID is " + "0000".substring(0, 4 - Math.ceil(Math.log(id+1)/Math.log(10))) + id + "."; } // window.onload handler // --------------------------------------------------------- /* Sets up the onclick handler for the button. */ window.onload = function() { b = document.getElementsByTagName('button')[0]; p = document.getElementsByTagName('p')[1]; if (b && p) { b.onclick = handler; } } })(); // End the function definition and execute it.