book-notes

Bulletproof Ajax

by Jeremy Keith

I, Michael Parker, own this book and took these notes to further my own learning. If you enjoy these notes, please purchase the book!

pg 8: A tiny, practically invisible inline frame, or hidden iframe, can get data from the server; Javascript can use that data to update the main page.
pg 9: Ajax isn’t tied to XML – you can use any structured format that carries data.

pg 19: Variables assigned null and 0 are treated as false in boolean expressions.
pg 24: Use === to check if two values are not just equal but identical; use !== to check if they are not identical.
pg 29: Functions can be assigned to variables; to store a reference to a function with arguments defined, use an anonymous function.
pg 31: Functions and methods belonging to a class are called methods and properties.
pg 32: Native objects are part of the core Javascript language; host objects are provided by the environment in which JavaScript is running.
pg 39: Calling getElementsByTagName("*") returns only element nodes, while the childNodes property contains text nodes and attributes.

pg 52: For XMLHttpRequest, the onreadystatechange event handler is triggered everytime the readyState property changes.
pg 55: The open method will not initiate a request; the send method must be invoked.
pg 56: If POSTing data, use the setRequestHeader method to set the Content-type header to application/x-www-form-urlencoded.
pg 57: Every browser finishes with a readyState value of 4 when the request is completed.
pg 59: If the server responds with MIME type text/xml or application/xml the response is in the responseXML property instead of responseText.

pg 73: Returned XML data can be traversed using the DOM methods you would use to traverse an HTML document.
pg 77: JSON, pronounced like the name Jason, does not need to be interpreted by JavaScript because it is JavaScript.
pg 80: The JSON stored in responseText is interpreted as an object literal and converted using the eval function.
pg 82: The send method of XMLHttpRequest can only access the domain serving up the Javascript file being executed.
pg 83: Using DOM scripting, you can dynamically create a script element with a Javascript URL from another domain; that script can modify your DOM.
pg 89: HTML fragments returned via Ajax can be inserted wholesale into your document by assigning the innerHTML property of an element.

pg 98: Use the onload event handler to invoke the DOM methods in your JavaScript only once the page has finished loading.
pg 103: After building a web page without Ajax, apply Ajax to scenarios where a page is reloaded but only partially modified.
pg 112: Given a form element, its elements property contains all its inputs.
pg 115: Do not rely on Javascript for form validation, but use it to get and display a validation response from the server.

pg 124: If you’re not going to try for graceful degradation, consider technologies beyond Ajax like Flash.
pg 126: Applications using Ajax should provide feedback to the user that some action is under way.
pg 130: It’s also good to show that something just happened, using something like the yellow fade technique.
pg 136: If the user would want to bookmark the changed state of a page, don’t replace full page refreshes with Ajax.
pg 137: With Ajax, wireframes representing web page must be ditched for prototypes that add dynamic elements through simple DOM scripting.

pg 141: Most screen readers don’t interact with the DOM, but take a snapshot of the document and put it in a “virtual buffer” for manipulation.
pg 143: Screen readers show a bias toward the creating or updating of tables, and focusable elements like form fields and links.
pg 143: Assign an element a tabindex of -1 to make it focusable and attract the screen reader without upsetting the default tab order.
pg 144: Put an opt-in checkbox off-screen that only screen-readers can find and toggle, which generates alert messages for Ajax updates.
pg 149: Web browsers can’t detect screen-readers, but Flash can, and can notify JavaScript of this.

pg 171: Functions within an object can access variables declared within the same object using closures.
pg 182: In the onreadystatechange method, display an error message with DOM scripting if the status code is not 200 or 304.
pg 184: Use setTimeout to call abort on the XMLHttpRequest object if the request is taking too long, and clearTimeout if the request completes.

pg 193: If you use a JavaScript library, consider its file size, as the client will need to download whatever you choose.