i am working with file upload and preview in angular 8.. i am able to preview word doc, image and pdf but not able to preview excel doc.. how can i do that.. i have tried with ngx-doc-viewer
preview(files) {
        if (files.length === 0)
            return;
        var mimeType = files[0].type;
        //if (mimeType.match(/image\/*/) == null) {
        //    this.message = "Only images are supported.";
        //    return;
        //}
        var reader = new FileReader();
        this.imagePath = files;
        reader.readAsDataURL(files[0]);
        reader.onload = (_event) => {
            this.imgURL = reader.result;
            this.myModel.show();
        }
    }
     <ngx-doc-viewer [url]="imgURL" viewer="mammoth"></ngx-doc-viewer>