I use js to assemble the data and then ajax to transmit it to the background. $request- > file () always cannot receive the file, and the file field passed by
is always converted into a string [object File] how to solve

foreground ajax code

onAjax(formObj,dataType)
    {
        var that = this;
        var form = $(formObj)[0];
        var data = this._formToData(form);
        var url = form.action;
        var type = form.method;
        $.ajax({
            sync : false,
            url : url ,
            data : data ,
            type : type ,
            dataType : dataType ? dataType : "json",
            success(r)
            {
                console.log(r);
            },
            complete(r)
            {
                console.log(r);
                var response = r.responseJSON;
                var status = r.status;
                if(status === 200)
                {
                    return that.showNotifies(response.msg,"success");
                }
                that._getResponseError(response.errors);
                return that.showNotifies(response.message,"danger");
            }
        });
        return false;
    },
    _formToData(form)
    {
        var i = 0;
        var data = [];
        for (i ; i < form.length ; i PP )
        {
            if(form[i].name)
            {
                if(form[i].type == "file")
                {
                    data.push({
                        name : form[i].name,
                        value : $(form[i])[0].files[0]
                    });
                }else{
                    data.push({
                        name : form[i].name,
                        value : form[i].value
                    });
                }
            }
        }
        return data;
    }

background code

public function edit($id,Request $request)
    {
        $this->_checkIsLoginUser($id);
        $user = User::find($id);


        $this->validate($request, [
            "firstName" => "nullable|max:10",
            "lastName" => "nullable|max:10",
            "contact" => "nullable|integer",
            "birthday" => "nullable|date|max:10",
            "address" => "nullable|string|max:200",
            "city" => "nullable|string|max:50",
            "country" => "nullable|string|max:50",
            "postal" => "nullable|integer",
            "aboutMe" => "nullable|string|max:255"
        ]);

        $path = $request -> file("avatar");
        $data = $request -> input();
        $data["avatar"] = $path;
        unset($data["_token"]);

        $user -> info = json_encode($data);
        $res = $user -> save();
        if($res)
        {
            return $this->_toAjax(__("notices.update.success"));
        }
        return $this->_toAjax(__("notices.update.danger"));
    }