HTMLInputElement.mozSetFileNameArray() - Web APIs
the htmlinputelement.mozsetfilenamearray() method sets the names of the files that selected on an html input element.
... syntax inputelement.mozsetfilenamearray(afilenames, alength); parameters afilenames is the array of file names to apply to the element.
... example var filearray = {"/foo/bar.txt", "/foo/foosball.txt"}; inputelement.mozsetfilenamearray(filearray, filearray.length); ...

Limitations of frame scripts
examples of apis add-on authors should avoid in frame scripts: nsifileinputstream nsifileoutputstream constructing a file from a string or nsifile (but file objects can be sent via message manager) htmlinputelement.mozsetfilenamearray (alternative: mozsetfilearray) xul and browser ui anything that tries to touch the browser ui or anything to do with xul is likely to not work in the content process.

Limitations of frame scripts
for example: nsifileinputstream nsifileoutputstream constructing a file from a string or nsifile (but file objects can be sent via message manager) htmlinputelement.mozsetfilenamearray (alternative: mozsetfilearray) file: uris, see bug 1187099 <...> xul and browser ui anything that tries to touch the browser ui or anything to do with xul is likely not to work in the content process.

HTMLInputElement - Web APIs
htmlinputelement.mozsetfilenamearray() sets the filenames for the files selected on the input.

Index - Web APIs
1742 htmlinputelement.mozsetfilenamearray() api, html dom, htmlinputelement, method, needsbrowsercompatibility, non-standard, reference the htmlinputelement.mozsetfilenamearray() method sets the names of the files that selected on an html input element.