js提交form数据的时候如果要包含file数据要用到FormData对象

$(document).ready(function() {
    $('#bookForm').submit(function(e) {
        e.preventDefault();

        if (this.checkValidity()) {
            const formData = new FormData(this);
            formData.append('action', 'handle_book_ajax');
            formData.append('param', 'create-book');

            $.ajax({
                type: 'POST',
                url: book_rest.ajax_url,
                data: formData,
                contentType: false,
                processData: false,
                success: function(res) {
                    console.log(res);
                    try {
                        const data = JSON.parse(res);
                        console.log("+success");

                        if (data.status) {
                            swal({
                                title: "Good Job",
                                text: data.message,
                                icon: "success"
                            }).then(() => {
                                $('#bookForm')[0].reset();
                            });
                        } else {
                            swal({
                                title: "Failed",
                                text: data.message,
                                icon: "error"
                            });
                        }
                    } catch (e) {
                        swal({
                            title: "Error",
                            text: '数据查询格式错误',
                            icon: 'error'
                        });
                    }
                },
                error: function(err) {
                    console.log(err);
                }
            });
        } else {
            console.log('Form has not been confirmed');
            swal({
                title: "Error",
                text: '请填写必要的表格字段',
                icon: 'error'
            });
        }
    });
});