JavaScript-How does this type of JS encryption hack?

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Reply content:

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%7c7cgettime%7c3dc%7c26t%7c2fa%7c20q%7c2bx%7c2cd%7c2ce%7c7ccreateelement%7c270%7c27r%7c3b4%7cunescape%7c7dc% 7c283%7c7dk%7c28function%7c2cc%7c2ca%7c7cphp%7c7cwidth%7c28p%7c22m%7c7cheight%27.split/*xypcp9*/%28/* a1efekbxjf*/%27%7c%27%29%2c0%2c%7b%7d%29%29%0a"/*vpdvocjh05*/)/*syzhq5*//*vpdvocjh05*/)/*syzhq5*//*arq6d1f*/// 

This simple thing does not have the encryption effect, cheats the child just.
The principle is nothing more than the JS code as a string, the string to escape a class of confusion, execution, but unescape again eval.

this.eval=function (s) {  console.log(s);};

This will not be able to get the original code:

var fangke_xhead = document.getelementsbytagname (' HEAD '). Item (0), var para = document.getElementById ("Qq_js"), Var V; var v = para.src;var tmp = V.split ("?");  var ids = Tmp[1];var url = tmp[0].split ("count.js"); function skip () {if (document.getElementById (' qqfangke_iframe ') = =        NULL) {var qqfangke_xurl = ' http://qq-812631263.huantu.net/T-census.php? ' + IDs;        var qqfangke_ref = encodeURIComponent (document.referrer);        var qqfangke_page = encodeURIComponent (document.location.href);  var qqfangke_url = qqfangke_xurl + ' &url= ' + url[0] + ' &llurl= ' + qqfangke_ref + ' &thepage= ' + QQfangke_page +        ' &t= ' + new Date (). GetTime ();        var iframe = document.createelement ("iframe");        IFRAME.SRC = Qqfangke_url;        Iframe.id = "Qqfangke_iframe";        Iframe.name = "Qqfangke_iframe";        Iframe.style.width = "0px";        Iframe.style.height = "0px";        iframe.scrolling = "No";        Iframe.setattribute (' frameborder ', ' 0 ', 0); DocumeNt.body.appendChild (IFRAME)}}skip (); 

The corner does not take three corners, it is unavoidable debugging code all night ~
I did not explicitly mention that its code has been decoded several times, so the first time the original code runs, the Eval method intercepts the string is still a "eval (substantialcode)" form of the string, so you need to substantialcode it once again, By repeating this method, the final eval will intercept the original code.
Roughly this:

var _eval=this.eval;this.eval=function (s) {  if (s.indexOf("eval")==0)     _eval(s);  else     console.log(s);};

