在 ajax 函数上遇到没有明显循环的无限循环 - Encountering an endless loop on an ajax function with no obvious loop

我有一个文件输入声明如下：

<input id = "front_photo" type = "file" name = "front_photo" onchange = "send_photo()" />

它调用的函数声明如下：

function send_photo ()
{
    var fileInput = document.getElementById('front_photo');
    var file = fileInput.files[0];
    var formData = new FormData();
    formData.append('front_photo', file);
    console.log("in");
    var ajaxHandler = new XMLHttpRequest();
    ajaxHandler.onreadystatechange = function ()
    {
        if(ajaxHandler.readyState == 4)
        {
            var picture_box = document.getElementById("polaroids_holder");
            var adder = document.getElementById("add_polaroid");
            var new_pic = document.createElement("div");
            new_pic.className = "polaroid";
            new_pic.style.backgroundImage = "url('/assets/img/temp_front/"+ajaxHandler.responseText+"')";
            picture_box.insertBefore(new_pic, adder);
            send_photo();
        }
    }
    ajaxHandler.open('POST', 'upload_polaroid', true);
    ajaxHandler.send(formData);
}

选择要上传一次的文件会导致它进入无限循环。我在顶部的"in"堆积在控制台日志中，所以我确定它是重复调用的函数本身，而不是服务器端重定向。此外，正在服务器上创建映像。这是PHP：

function upload_polaroid ()
    {
        if(isset($_FILES['front_photo']))
        {
            $format = explode(".", $_FILES["front_photo"]["name"]);
            $format = $format[1];
            $filename = md5(mt_rand().microtime(true)).".".$format;
            $allowedTypes = array("image/tiff", "image/gif", "image/jpeg", "image/png", "image/x-bmp", "image/x-ms-bmp", ".bmp", ".dib", "image/vnd.microsoft.icon", "image/x-xbitmap", "image/x-xbm", ".xbm", ".cur");
            if(in_array($_FILES["front_photo"]["type"], $allowedTypes))
            {
                if(file_exists(getcwd()."/assets/img/temp_front/".$filename)) 
                {
                    chmod(getcwd()."/assets/img/temp_front/".$filename,0755);
                    unlink(getcwd()."/assets/img/temp_front/".$filename);
                }
                move_uploaded_file($_FILES["front_photo"]["tmp_name"], getcwd()."/assets/img/temp_front/".$filename);
                $image_path = "/assets/img/temp_front/".$filename;
                echo $image_path;
            }
            else
            {
                echo "File is not of a valid image type."; die;
            }
        }
        else
            die; //var_dump($_FILES);
    }

这里可能出了什么问题？

当 ajax 请求成功时，代码将调用 send_photo(); 这将触发另一个 ajax 请求，并在成功时再次调用 send_photo(); 方法。这会导致代码递归。

function send_photo ()
{
    var fileInput = document.getElementById('front_photo');
    var file = fileInput.files[0];
    var formData = new FormData();
    formData.append('front_photo', file);
    console.log("in");
    var ajaxHandler = new XMLHttpRequest();
    ajaxHandler.onreadystatechange = function ()
    {
        if(ajaxHandler.readyState == 4)
        {
            var picture_box = document.getElementById("polaroids_holder");
            var adder = document.getElementById("add_polaroid");
            var new_pic = document.createElement("div");
            new_pic.className = "polaroid";
            new_pic.style.backgroundImage = "url('/assets/img/temp_front/"+ajaxHandler.responseText+"')";
            picture_box.insertBefore(new_pic, adder);
            /***********************************************/
            send_photo();  //this is making the code recursive
        }
    }
    ajaxHandler.open('POST', 'upload_polaroid', true);
    ajaxHandler.send(formData);
}

通过在文档中插入new_pic来证明成功之后，您直接从 ajax 回调调用 send_photo 函数。这样，它将永远一次又一次地上传所选文件。