Use of the Document Head by HTML coding

These browsers are limited to Internet Explorer 3 and later. Telling Non-JavaScript Browsers to Ignore Your Code not all browsers support JavaScript. Older browsers, such as Netscape Navigator1, Internet Explorer 2, and the character-based Lynx browsers do not recognize the script tag, as a consequence, display as text all. Fortunately, HTML provides a method to conceal JavaScript statements from such JavaScript –challenged browsers. The trick is to use HTML comments tags to surround the JavaScript statement .Because HTML comments are displayed only within the code used to create a web page; they do not show up as part of the browser’s display.

The comment tags because the JavaScript statement to be treated as comments by JavaScript –challenged browsers. JavaScript enabled browsers, on the other hand, know to ignore the comment tag and process the enclosed statement as JavaScript. The No script Tag Version 2 and later of Netscape Navigator and version 3 and later of Microsoft Internet Explorer support JavaScript. These browsers are account for nearly 90 percent of browser use on the web and their percentage of use is increasing. This means that most browser requests come from JavaScript –capable browsers. However, there are still popular browsers, such Linex, that do not support JavaScript. In addition of disabling JavaScript the tag was created for those browsers that can’t or won’t process JavaScript. It is used to display markup that is an alternative to executing a script. The HTML instructions contained inside the tags are displayed by java script-challenged browsers. The Script Tag’s SRC Attribute The script tag itself provides another way to include JavaScript code in an HTML document, via the tag’s SRC attributes, which may be used to specify a file containing JavaScript Java Script Entities JavaScript entities allow the value of an HTML attribute to be proved by a JavaScript expression. This allows attributes value to be dynamically calculated during the loading of a web page. A JavaScript entity begins with &(and ends with);. JavaScript Comments.

The JavaScript language provides comments of its own. These comments are use to insert notes and processing description into scripts. The comments are ignored when the statements of a script are parsed by JavaScript –enabled browsers. JavaScript comments use the syntax of C++ and Java. The string identifiers a comment that continue to the end of the line. The script contain four statements the use of JavaScript comments. The script contains four that, if they weren’t ignored, would write various capitalizations of that text Hello World. To the current document. However, since the first three statements are contained in comments, and since browsers ignore comments, these statements have no effect on the web page generated by the script Use of the Document Head The head of an HTML document provides a great place to include JavaScript definitions. Since the head of document is processed before its body, placing definition in the head will cause them to be defined before they are used. This is important because any attempt to use a variable before it is defined result in error. The script contained in the document head defines a variable named greeting and sets its value to the sprig. The script contained in the document’s body then writes the value of the greeting variable to the current document.

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