What does document.write() do?

Question

This is a very basic question. I have this script:

    <script type="text/javascript">
        function write(){
            document.write('Hello2')
        }
        write();
    </script>

It shows my complete page. And at the end of page Hello2 will be displayed. But when ever I go to developer tools and call write(), it will replace my entire body html. Just curious to know.

        window.onload=write;// has the same effect. Clear's my page.

Thanks.

Answer 1

When the document is being read and parsed by the browser, if there's a script element that calls document.write, the output of document.write is inserted into the document at that point. Later, though, once the page is fully loaded, if you use document.write, it implicitly performs a document.open, which wipes out the page and starts writing a new one from scratch.

More on MDN:

• document.write
• document.open

In general, rather than using document.write to add content to a page, use the various DOM methods (either directly, or via a library like jQuery, YUI, Closure, or any of several others).