History of the DOM
In the early days of the Web, browser vendors such as Netscape and Microsoft developed
their own distinct ways of accessing parts of a web page. In the beginning, they tended to
focus on common page elements such as images, links, and forms. These methods became
known as DOM level 0, or legacy DOM. Some of the more common methods can still be
used in the current DOM API.
The World Wide Web Consortium (W3C) started to standardize the process and created the
DOM API level 1 in 1998. This introduced a complete model for web pages that allowed
every part of them to be navigated.
The DOM level 2 was published in 2000 and introduced the popular getEle-
mentById() method, which made it much easier to access specific elements on a web
The current standard is DOM level 3, although level 4 is in the process of being developed
as a living standard, which means that it is being implemented in browsers before it is form-
alized and published.
Despite the standardization process, browsers have not always implemented the DOM con-
sistently so it has been difficult to program for in the past. Fortunately, since Internet Ex-
plorer 8, DOM support has been much more consistent and most modern browsers imple-
ment the current DOM level 3 API reasonably well. They are also implementing more of
the new DOM level 4 features with every update.
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