Created
May 29, 2012 07:00
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Jessie and conditional comment proposal design problem
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| <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> | |
| <html> | |
| <head> | |
| <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> | |
| <title>Title</title> | |
| </head> | |
| <body> | |
| <script src="jessie.js"></script> | |
| <!--[if lte IE 8]><script src="jessie-ie8-and-below.js"></script><![endif]--> | |
| </body> | |
| </html> |
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| (function(global) { | |
| var globalDocument = global.document, | |
| isHostObjectProperty = function(object, property) { | |
| return !!(typeof(object[property]) == 'object' && object[property]); | |
| }, | |
| isHostMethod = function(object, method) { | |
| var type = typeof object[method]; | |
| return type == 'function' || | |
| type == 'object' && !!object[method] || | |
| type == 'unknown'; | |
| }, | |
| html = isHostObjectProperty(globalDocument, 'documentElement') && globalDocument.documentElement, | |
| canCall = !!Function.prototype.call; | |
| /* | |
| Description: | |
| Relies on Microsoft's `el.attachEvent` implementation for IE8- | |
| */ | |
| /* | |
| Support: | |
| IE6, IE7 | |
| */ | |
| var attachListener; | |
| attachListener = function(el, eventType, fn) { | |
| var listener = function() { | |
| var e = window.event; | |
| fn.call(e, e); | |
| }; | |
| el.attachEvent('on'+eventType, listener); | |
| // Discard unneeded references | |
| // Prevents circular references with host objects (e.g. the element) | |
| // Prevents IE leaks related to such circular references | |
| // No unload event cleanup required | |
| el = null; | |
| return listener; | |
| }; | |
| global.jessie = { | |
| isHostMethod: isHostMethod, | |
| isHostObjectProperty: isHostObjectProperty, | |
| attachListener: attachListener | |
| } | |
| globalDocument = html = null; | |
| })(this); |
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| (function(global) { | |
| var globalDocument = global.document, | |
| isHostObjectProperty = function(object, property) { | |
| return !!(typeof(object[property]) == 'object' && object[property]); | |
| }, | |
| isHostMethod = function(object, method) { | |
| var type = typeof object[method]; | |
| return type == 'function' || | |
| type == 'object' && !!object[method] || | |
| type == 'unknown'; | |
| }, | |
| html = isHostObjectProperty(globalDocument, 'documentElement') && globalDocument.documentElement, | |
| canCall = !!Function.prototype.call; | |
| /*global canCall */ | |
| /* | |
| Description: | |
| Relies on `unction.prototype.bind` | |
| */ | |
| var bind; | |
| if(canCall && Function.prototype.bind){ | |
| bind = function(fn, thisObject) { | |
| return fn.bind.apply(fn, Array.prototype.slice.call(arguments, 1)); | |
| }; | |
| } | |
| /*global bind,attachListener */ | |
| /* | |
| Description: | |
| Relies on `jessie.bind` and `jessie.attachListener` | |
| */ | |
| var attachBoundListener; | |
| if(bind && attachListener) { | |
| attachBoundListener = function(el, eventType, fn, thisObject) { | |
| var listener = bind(fn, thisObject); | |
| thisObject = null; | |
| return attachListener(el, eventType, listener); | |
| }; | |
| } | |
| global.jessie = { | |
| isHostMethod: isHostMethod, | |
| isHostObjectProperty: isHostObjectProperty, | |
| bind: bind, | |
| attachBoundListener: attachBoundListener | |
| } | |
| globalDocument = html = null; | |
| })(this); |
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There is a problem here: attachBoundListener is defined before attachListener is defined.
Also each of the individual feature tests i.e. if(bind && attachListener) {....... are checked against locally scoped variables. This means that even if we could (by placing ie8 conditional comments before main file) get ie8-and-below.js to run first they would only be defined and exposed to the world as "jessie.attachListener" and not "attachListener".