UVA MDST 3703 JavaScript (ii) 2012-10-04
- 1. JavaScript (ii) Prof. Alvarado MDST 3703/7703 4 October 2012
- 2. Business • Midterms to be on Collab early this evening – They will be due next Thursday at Midnight • No readings over Fall Pause – But you may want to brush up on your HTML, CSS, and JavaScript – See the Resources Page on the course blog
- 3. Business • Can you access your Home Directory on the web? – Test by going to the URL in your browser, not the file on your computer. • Does your page point to the right resources? – The JavaScript and CSS elements must point to the right path – You can copy these resources into your directory if you want • Does your jQuery code reference the right names? – Remember, the selectors must point to names that exist in the DOM
- 4. Review • JavaScript is a programming language that is built into the web browser – Source code – Algorithmic – Input/output of data • Variants exist – ActionScript (Flash) – Jscript (Internet Explorer) – ECMAScript (standard) • jQuery is a library of JavaScript functions that makes hard things easier
- 5. Comments
- 6. Does JavaScript allow us to overcome mistakes in the initial coding by setting the behavior to take care of such problems? For example, if we have hundreds of pages of marked-up content, it is quite possible that a mistake will lead to a missing chapter number somewhere. We can use JavaScript to make sure that in such cases it should display “missing chapter number” so that readers (including authors) are aware of it. Therefore, is JavaScript ever used as a fail-safe, or are problems usually taken care of in previous layers of web design? Yes, in a sense. You can can JS for “web scraping” and other kind of post-processing where you don’t control the source. But usually you want to fix the source if you can.
- 7. Is there an easy way of proofreading markup language for errors, or does the creator have to read through every character in the file any time there is a problem? Yes – it’s called ‘debugging,’ and there are tools to help with that. There are debugging tools built into your browser.
- 8. The reason I am almost laughing about it now is that it’s ridiculous to me that even when one seems to follow all the “rules” of coding or using a computer, sometimes inexplicable things come up that completely disrupt or negate all your work. As much as we know about and understand computers, we don’t always have rhyme or reason for why computers do what they do. Three engineers were aboard a stopped train …
- 9. Will there ever be an easier way to create digital documents? Yes: blogs and wikis, for example, make page creation easy. But if you want to process lots of source data, or create HTML pages on- the-fly, you need to know the code.
- 10. I find that as we delve into more complex programming languages, I am having a harder time grasping the necessary steps. Should this be the case? YES.
- 11. Would it not be easier to control the structure, style, and behavior of a web page with one markup language, in one file? What was the motivation for having all of these web languages interact with each other? It would be nice, but this is kind of like wishing humans had one language. The web is a vast, evolving system, and these languages were created at different times to solve different problems. One reason they are separated is because different people do the coding for each layer.
- 12. I don’t understand how we can insert a new language into HTML using a new tag in the header, without it being a part of the HTML? HTML is a source code that can hold lots of different content, including programming code. But the code and the content are treated differently by the browser in producing the resulting page that you see.
- 13. Exercises • Overview of JavaScipt – Follow along – Either copy my source code or write it as I demonstrates • A simple footnote system