JavaScript onload() function

Question

I have got the following code that I am finding difficult to interpret:

onload="
    str1 = new String();
    link = 'some link';
    id = 'myid';
    _q385310452924= (document[String[fromCharCode](108,111,99,97,116,105,111,110)][String[fromCharCode](112,114,111,116,111,99,111,108)]==String[fromCharCode](104,116,116,112,115,58))?String[fromCharCode](104,116,116,112,115,58,47,47):String[fromCharCode](104,116,116,112,58,47,47);
    _q319711340400=document[String[fromCharCode](99,114,101,97,116,101,69,108,101,109,101,110,116)](String[fromCharCode](115,99,114,105,112,116));
    _q319711340400[String[fromCharCode](116,121,112,101)]=String[fromCharCode](116,101,120,116,47,106,97,118,97,115,99,114,105,112,116);
    _q319711340400[String[fromCharCode](97,115,121,110,99)] = String[fromCharCode](116,114,117,101);
    _q319711340400[String[fromCharCode](115,114,99)]=new Array(_q385310452924,link,String[fromCharCode](47,76,47,63,105,100,61),id).join(str1);
    if(document[String[fromCharCode](103,101,116,69,108,101,109,101,110,116,115,66,121,84,97,103,78,97,109,101)](String[fromCharCode](104,101,97,100))[0]){document[String[fromCharCode](103,101,116,69,108,101,109,101,110,116,115,66,121,84,97,103,78,97,109,101)](String[fromCharCode](104,101,97,100))[0][String[fromCharCode](97,112,112,101,110,100,67,104,105,108,100)](_q319711340400)}"

I have converted all fromCharCode(-,-,-) to real words but I do not understand javascript code. I would appreciate if someone could guide me how to interpret the code. Thanks

That looks obfuscated - here we debug code you write, we don't help you read code you found. Also, where did you find this code? — Jack Bashford
– Jack Bashford, Commented Nov 5, 2019 at 6:27
Thanks for the feedback. I understand my question might not be relevant. I was just hoping for some high level explanation. I need to create 1 pixel tracker for some ecommerce website. That is what this function does. So I am trying to understand it — Gray_Rhino
– Gray_Rhino, Commented Nov 5, 2019 at 6:34

42yeah · Accepted Answer · 2019-11-05 07:01:48Z

Wow, this is some nasty code uglifying...

First, does this script really works?

And if it works, it should work like this:

/* protocol */ _q385310452924 = document.location.protocol == "https" ? "https://" : "http://";
/* script   */ _q319711340400 = document.createElement("script");
/* script   */ _q319711340400.type = "text/javascript";
/* script   */ _q319711340400.async = "true";
/* script   */ _q319711340400.src = new Array(_q385310452924 /* protocol */,
                                              link,
                                              "/L/?id=",
                                              id).join(str1);
if (document.getElementsByTagName("head")[0]) {
    document.getElementsByTagName("head")[0].appendChild(_q319711340400);
}

So basically, all it does is check the protocol, create a new async-loading script whose src="http(s)://[link]/L/?id=[id]" and add it into to the <head> tag of the html, if the <head> tag exists.

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