JavaScript: The Definitive Guide, Fourth Edition

The Location Object

The location property of a window is a reference to a Location object -- a representation of the URL of the document currently being displayed in that window. The href property of the Location object is a string that contains the complete text of the URL. Other properties of this object, such as protocol, host, pathname, and search, specify the various individual parts of the URL.

The search property of the Location object is an interesting one. It contains any portion of a URL following (and including) a question mark. This is often some sort of query string. In general, the question-mark syntax in a URL is a technique for embedding arguments in the URL. While these arguments are usually intended for CGI scripts run on a server, there is no reason why they cannot also be used in JavaScript-enabled pages. Example 13-5 shows the definition of a general-purpose getArgs( ) function that you can use to extract arguments from the search property of a URL. It also shows how this getArgs( ) method could have been used to set initial values of the bouncing window animation parameters in Example 13-4.

Example 13-5. Extracting arguments from a URL

/* * This function parses comma-separated name=value argument pairs from * the query string of the URL. It stores the name=value pairs in * properties of an object and returns that object. */ function getArgs( ) { var args = new Object( ); var query = location.search.substring(1); // Get query string var pairs = query.split(","); ...