tailieunhanh - JavaScript Bible, Gold Edition part 140

JavaScript Bible, Gold Edition part 140. This book will bring programmers and non-technical professionals, including casual programmers and scripters, painlessly up to speed on all aspects of mastering JavaScript. Key topics include programming fundamentals, JavaScript language elements and how to use them effectively, and how to easily and efficiently add powerful new functionality to HTML documents and Java applets. | Security and Netscape Signed Scripts The paranoia levels about potential threats to security and privacy on the Internet are at an all-time high. As more people rely on e-mail and Web site content for their daily lives and transactions the fears will only increase for the foreseeable future an indeterminate number of Web Weeks . As a jokester might say though I may be paranoid but how do I know someone really isn t out to get me The answer to that question is that you don t know and such a person may be out there. But Web software developers are doing their darnedest to put up roadblocks to those persons out to get you hence the many levels of security that pervade browsers. Unfortunately these roadblocks also get in the way of scripters who have completely honest intentions. Designing a Web site around these barriers is one of the greatest challenges that many scripters face. Battening Down the Hatches When Navigator 2 first shipped to the world way back in February 1996 it was the first browser released to include support for Java applets and scripting two entirely different but often confused technologies. It didn t take long for clever programmers in the Internet community to find the ways in which one or the other technology provided inadvertent access to client computer information such as reading file directories and Web surfer activities such as histories of where you ve been on the Net and even the passwords you may have entered to access secure sites . JavaScript in particular was the avenue that many of these programmers used to steal such information from Web site visitors browsers. The sad part is that the same features that provide the access to the information were intentionally made a part of the initial language to aid scripters who would put In This Chapter Exploring browser security policies Applying JavaScript to Navigator security mechanisms Using Netscape signed scripts 1240 Part V Putting JavaScript to Work those features to beneficial use in