I'm working through a small file upload script (learning experience) and I noticed that when selecting microsoft office related files (.doc or .docx for example) the file objects do not have a type specified:

For .doc files I had expected the type to be "application/msword" and along the same train of thought .docx to be "application/vnd.openxmlformats-officedocument.wordprocessingml.document".

In the cases when the type cannot be determined is the correct course of action to look at the file extension and match that to the "expected" content / mime type?

Sample script:

<div id="fileUpload">
    <input type="file" id="fileElem" style="display:none;" onchange="handleFiles(this.files)"/>
    <a href="#" id="fileSelect">Select some files</a>
</div>

<script type="text/javascript">
    var fileSelect = document.getElementById("fileSelect"),
        fileElem = document.getElementById("fileElem");

    fileSelect.addEventListener("click", function (e) {

        if (fileElem) {
            fileElem.click();
        }

        e.preventDefault();
    }, false);

    function handleFiles(files) {
        console.log(files);
    }

</script>