CODEWITHSUNDEEP
javascriptmemory-leaksxmlhttprequest
request
request

Reputation: 1

Memory-leak at a wrapped XMLHttpRequest function

I wrote the following :

function ao(){
this.count=0;
this.flag=0;
this.tmr=0;
var self = this;
this.make=function(){
    //log("before: "+this.url+" "+this.xhr);
    self.xhr = (window.XMLHttpRequest)
        ? new XMLHttpRequest() : new ActiveXObject('Microsoft.XMLHTTP');
    //log("after: "+this.xhr);
}
this.request = function (method, url, sendStr, delay){
    this.delay=delay;
    if(delay && self.tmr==0){
        self.start();
    }
    if(self.flag==0){
        this.method = method;
        this.url = url;
        this.sendStr = sendStr;
        self.make();
        this.xhr.open(method, url, true);
        this.xhr.onreadystatechange = this.stateChange;
        this.xhr.onabort=this.rrr;
        this.xhr.onerror=this.rrr;
        this.xhr.setRequestHeader("Cache-Control","no-cache");
        this.xhr.send(sendStr);
    }
};
this.repeat=function(){
    if(this.flag==0){
        this.flag=1;
        this.count++;
        this.xhr.open(self.method, self.url+"?"+this.count, true);

        this.xhr.onreadystatechange = this.stateChange;
        this.xhr.onabort=this.rrr;
        this.xhr.onerror=this.rrr;
        this.xhr.setRequestHeader("Cache-Control","no-cache");

        this.xhr.send(self.sendStr);
    }
    return 0;
}
this.stop=function(){
    window.clearInterval(this.tmr);
    this.tmr=0;
    this.flag=0;
}
this.start =function(){
    self.tmr=window.setInterval(function(){self.repeat();},self.delay);
}
this.stateChange = function(){
    if (self.xhr.readyState <= 1){
        return;
        self.log("404 errors");
    } else {
        if (self.xhr.readyState == 4 && self.xhr.status == 200){
            self.resp = self.xhr.responseText;
            if (self.callback != null)
                self.callback(self.xhr.readyState, self.xhr.status);
            else {
                if (self.getHTML) {
                    self.getHTML(self.resp);
                    this.xhr=null;
                } else {
                    if (self.xhr.readyState == 4 && self.xhr.status == 200){
                        self.parseJSON();
                        self.traverse();
                        this.ro=null;
                        this.xhr=null;
                    }
                }
            }
        }
    }
    self.flag=0;
    return 0;
};

and in windows ff there is a memory leak. I spent days trying to fix it, but I'm stumped.

The following works :

var x=new ao();
ao.request("POST","/cgi-bin/sdf.cgi","text",1000)

and after every 1000 miliseconds if previous request is done, it makes new request.

Upvotes: 0

Views: 1233

Answers (1)

CoR
CoR

Reputation: 3914

Developers should also take precautions when it comes to using the onreadystatechanged event of an XMLHttpRequest object. If the handler is a closure that closes over a reference to the same XMLHttpRequest object, another circular dependency can be created. This isn't necessairly detected by the above tool because the object is not part of the DOM. Link

Upvotes: 4

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