无法将其转换为content-type：application / json

Question

let formData2 = new FormData();
                    formData2.append('_token', vm.response._token);
                    formData2.append('file', vm.response.content[i].path);
                    formData2.append('type', vm.response.content[i].type);

                        // this part is progress bar

                            var xhr = new XMLHttpRequest();
                            xhr.open("POST", "page/file/create/upload", true);
                            if (xhr.upload) {
                                xhr.upload.onprogress = function (e) {
                                    if (e.lengthComputable) {
                                        progressBar.max = e.total;
                                        progressBar.value = e.loaded;
                                        display.innerText = Math.floor((e.loaded / e.total) * 100) + '%';
                                    }
                                }
                                xhr.upload.onloadstart = function (e) {
                                    progressBar.value = 0;
                                    display.innerText = '0%';
                                }
                                xhr.upload.onloadend = function (e) {
                                    progressBar.value = e.loaded;
                                }
                            }
                            xhr.send(formData2);

我按下f12后在网络选项卡中看到，在响应标题中，我的内容类型是text / html。我认为这是获得500错误的主要原因。因为在ajax中需要JSON。我正在使用laravel，我的控制器得到NULL。那怎么能把它变成json呢？

Answer 1

let formData2 = new FormData();
                    formData2.append('file', vm.response.content[i].path);
                    // this part is progress bar

                    var xhr = new XMLHttpRequest();
                    xhr.open("POST", "page/file/create/upload", true);
                    xhr.setRequestHeader('Content-Type', 'application/json; charset=utf-8');
                    xhr.setRequestHeader('X-CSRF-TOKEN', vm.response._token);

                    if (xhr.upload) {
                        xhr.upload.onprogress = function (e) {
                            if (e.lengthComputable) {
                                progressBar.max = e.total;
                                progressBar.value = e.loaded;
                                display.innerText = Math.floor((e.loaded / e.total) * 100) + '%';
                            }
                        }
                        xhr.upload.onloadstart = function (e) {
                            progressBar.value = 0;
                            display.innerText = '0%';
                        }
                        xhr.upload.onloadend = function (e) {
                            progressBar.value = e.loaded;
                        }
                    }
                    xhr.send(formData2);

@ksoni仍然得到500错误代码。而content-header仍然是text / html。我用formData2（图像或任何文件）做了什么错误。什么是程序。你能解释一下吗？