Thursday, August 11, 2011

A few notes on JavaScript

I am one the 99% of the world who has long nursed the misconception that JavaScript has something to do with Java. And why not? The name sort of implies it.

It was only after I searched without success on the Java Tutorial site for some mention of JavaScript that I stumbled across the knowledge that JavaScript was in fact developed by Netscape, under the name LiveScript. Armed with that knowledge, it is not surprising to find the best reference information on Mozilla site.

According to Wikipedia, the nonsensical name choice had something to do with Netscape wanting to cash in on the popularity and cachet of Java, and Sun wanting support for Java technology in the then popular Netscape browser.

For a while only the Netscape family of browsers supported JavaScript. Microsoft later produced what it calls JScript to run in its browser. JScript is similar but not identical to Javascript.

According to Foldoc JavaScript runs a hundred times slower than C, and ten times slower than Java.

According to Wikipedia:

JavaScript very quickly gained widespread success as a client-side scripting language for web pages [and] has become one of the most popular programming languages on the web. Initially ... many professional programmers denigrated the language because its target audience was web authors and other such "amateurs" ... The advent of Ajax returned JavaScript to the spotlight and brought more professional programming attention.

So what is Ajax? The link is to another Wiki page, which gives lots of details, but I'll quote a bit of the history, as it mentions Applets:

In the 1990s, most web sites were based on complete HTML pages; each user action required that the page be re-loaded from the server (or a new page loaded) ... Asynchronous loading of content first became practical when Java applets were introduced in the first version of the Java language in 1995. These allow compiled client-side code to load data asynchronously from the web server after a web page is loaded.

But as I have reported in previous posts, Applets are fraught with difficulties. This brings me back to the definition of Ajax, which is an acronym for "asynchronous JavaScript and XML"

In summary, JavaScript is a scripting language used in web pages in conjunction with other languages and technologies to achieve ends more complex than can be achieved with simple HTML. The language looks a bit like Java (and C) and meshes with Java, but it was developed independently by the creators of the Netscape browser.

1 comment:

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