Pass a value in document.write

I have a <script> that creates a tagId value.

Currently, it will display as document.write(tagId);

I want to place tagId in a <form> as:

<input type="text" name="" value="tagId">

Example, something like:

document.write(< input type="text" name="" value="tagId" >);

How can I place the tagID value to insert in the text form?