问在IE中设置文件输入标记的.files时出错

EN

var file = document.getElementById("file");
file.onchange = function(){
    var ext = this.value.match(/\.([^\.]+)$/);
    if(ext!=null && ext.length>1){
        switch (ext[1].toLowerCase()) {
            case 'doc':
            ...
                if (file.files.length > 0) {
                    appendFile(file.files);
                }
                break;
            default:
                alert('Sorry, files of type .' + ext[1].toLowerCase() + " are not allowed.");
                this.value = '';
        }
    }
};

function appendFile(files){
    ...
    if(files.length>0){
        file = files[0];
        ...
        htmlFile.appendChild(createFileInput(files));
        ...
        parentDiv.append(htmlFile);
    }
}

function createFileInput(files){
    fileInput = document.createElement("input");
    fileInput.setAttribute('type','file');
    fileInput.files=files;
    fileInput.classList.add('files');
    fileInput.style.display = 'none';
    return fileInput;
}