异步上传图片

var fd = new FormData(document.getElementById("file-form"));               
url: "scmCarrier/upload/${scmCarrier.carrierId}",
                type: "POST",
                data: fd,
                enctype: 'multipart/form-data',
                processData: false,  // tell jQuery not to process the data
                contentType: false   // tell jQuery not to set contentType