Understanding JavaScript (and Its History)
| JavaScript is a client-side scripting languagethat means a language that runs on the client side, within a web browser. (JavaScript can also be used on the server side and otherwise outside a browser, but this is not of interest for the purpose of this book.) If the browser supports the language, JavaScript grants access to the current page and lets the script determine properties of the client, redirect the user to another page, access cookies, and do much more. The birth of JavaScript was in September 1995, when version 2.0 of the Netscape browser was released, the first version to come with the scripting language. Back then, the name of the language was first Mocha and then, when released, LiveScript; but Netscape made a marketing deal with Sun (creator of Java) and renamed the language to JavaScript in December of that year. The concept received a large following, so Microsoft included JavaScript support from Internet Explorer version 3 onward (mid-1996). For legal reasons, the Microsoft flavor of the language was called JScript. JScript was more or less compatible with JavaScript, but started to include additional, IE-only features (thatapart from some exceptionsnever really caught on). In 1997, the standard ECMAScript (ECMA-262) was published; JavaScript is therefore the first implementation of that standard. The standard itself specifies only the language, but not features of the surrounding hosts (for instance, how to access the current browser window or open a new one). ECMAScript became an ISO norm in 1998. Around 1997 or 1998, the browser war between Netscape and Microsoft reached a climax, with both vendors adding new, incompatible functionality to version 5 of their browsers. The rest is history: Netscape scrapped the idea of releasing browser version 5 and decided to start all over with Netscape 6, which helped Internet Explorer to expand its market share to over 90%. It took the then-founded Mozilla project several years to come to life again. The very popular Firefox browser was based on Mozilla and started to take market share away from Microsoft. From the JavaScript point of view, not very much has happened in the past few years. Firefox 1.5, which was released in late 2005, supports the new JavaScript version 1.6, but changes are rather minimaland Internet Explorer is far away from supporting that. But with Internet Explorer 7 and Firefox 2.0 in the foreseeable future (and both already available in a preview version), it's an interesting time for a web developer. Other browsers, by the way, support JavaScript as well. Differences are subtle, but still can be extremely annoying when one is developing a browser-agnostic web application. Among the browsers that currently support JavaScript are the following:
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