Created
July 3, 2015 15:08
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annotated pixel script
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| //declaring an anonymous self executing function | |
| //this function is declared and immediately executed | |
| //@Parameters - t= window, e= document | |
| ! function(t, e) { | |
| // if FQTag is not present in window object already, initialize it with following function | |
| // the argument to this function 'o' is of the form as shown below- | |
| // { | |
| // "org": "keswu4ug7detrumayur3", | |
| // "s": "${AUCTION_ID}", | |
| // "p": "${SELLER_MEMBER_ID}", | |
| // "a": "${SITE_ID}", | |
| // "cmp": "${CREATIVE_ID}", | |
| // "fmt": "banner", | |
| // "rd": "URL", | |
| // "ctu": "CTURL", | |
| // "ad": "ElementID", | |
| // "rt": "display", | |
| // "sl": "1", | |
| // "fq": "1" | |
| // } | |
| t.FQTag = t.FQTag || function(o) { | |
| var n, r = t.encodeURIComponent, | |
| i = ["s", "r", "c"].join(""), // i = "src" | |
| a = ["i", "n", "n", "e", "r", "H", "T", "M", "L"].join(""), // a= "inneHTML" | |
| l = ["aux=1"], | |
| s = "http://fqtag.com/pixel", | |
| d = "s" + Math.floor(1000000001 * Math.random()); // random string of the form s2093482034 | |
| //populating the passed object with more properties | |
| o.iif = t.top.location != t.location, //boolean- if the script is inside an iframe or the main page? | |
| o.rf || (o.rf = e.referrer), // string - domain from where did i arrive this page from | |
| //if the length of the above URI is greatere than 1000, and it does not contain any query params, extract the initial part before query params | |
| //as we might not be interessted in the latter part | |
| o.rf.length > 1e3 && (o.rf.indexOf("?") > -1 ? o.rf = o.rf.split("?")[0] : o.rf.indexOf("%3F") && (o.rf = o.rf.split("%3F")[0])), | |
| // URL of the current page/iframe, the script is in | |
| o.loc || (o.loc = e.location), | |
| // same logic as above, trim this URL if too long | |
| o.loc.length > 1e3 && (o.loc.indexOf("?") > -1 ? o.loc = o.loc.split("?")[0] : o.loc.indexOf("%3F") && (o.loc = o.loc.split("%3F")[0])), | |
| // timestamp plus random string - used as a UUID whenever this script executes | |
| o.s = o.s || (new Date).getTime().toString(36) + "-" + Math.floor(4294967296 * (1 + Math.random())).toString(16).substring(1); | |
| //iterate over all properties of the object o | |
| for (var c in o) | |
| // push each property and value in the array l as a string in the form of propertyName=propertyValue | |
| // if a property called "rt" is present , skip it, and instead, initialize the variable n with its value | |
| o.hasOwnProperty(c) && ("rt" === c ? n = r(o[c]) : l.push(r(c) + "=" + r(o[c]))); | |
| //if n isstill not initialized, in case "rt" was not present in o, initialize it with "click" | |
| // in this example however, it was present and its value was "diaplay" | |
| n = n || "click", | |
| // make a long string by concatenating all elements of array l | |
| // so basically l is a string representation of the full object o now | |
| l = l.join("&"); | |
| //function which takes two arguments t and e | |
| // t is a script tag | |
| // e is a function | |
| // the calls e (if passed) when script t is fully loaded | |
| var f = function(t, e) { | |
| var o = !1; //false | |
| t.onload = t.onreadystatechange = function() { | |
| o || this.readyState && "loaded" != this.readyState && "complete" != this.readyState || (o = !0, t.onload = t.onreadystatechange = null, e && e()) | |
| } | |
| }, | |
| // create a div tag | |
| h = e.createElement("div"); | |
| // initialize it one pixel tall and wide (basically this is what we call as pixel) | |
| h.style.height = h.style.width = "1px", h.style.bottom = h.style.right = "0", h.style.position = "absolute", h.style.pointerEvents = "none"; | |
| //create a script tag | |
| var p = e.createElement("script"); | |
| //asign it the source attribe as - | |
| // (random string d) (rt) | |
| // | | | |
| //http://fqtag.com/pixel.js?cId=s90808008&rt=js&irt=display& (the whole o obj properties as key=value) | |
| p[i] = s + ".js?cId=" + d + "&rt=js&irt=" + n + "&" + l, | |
| // pass this script tag to function f to load it | |
| f(p); | |
| var m = "__sp_iframe_" + Math.floor(1000000001 * Math.random()), | |
| y = s + "?rt=" + n + "&" + l; // y = http://fqtag.com/pixel?rt=display& (the whole o obj properties as key=value) | |
| // put an iframe inside the pixel div h | |
| // <iframe id="__sp_iframe_29384723947" src="http://fqtag.com/pixel?rt=display& (the whole o obj properties as key=value)" name="__sp_iframe_29384723947" style="border:0;height:1px;margin:0;padding:0;width:1px"></iframe> | |
| // this will put a pixel on the page | |
| h[a] = '<iframe id="' + m + '" src="' + y + '" name="' + m + '" style="border:0;height:1px;margin:0;padding:0;width:1px"></iframe>'; | |
| // function g | |
| // checks if the document is loaded, if not retries until it is loaded (body tag present on page) | |
| // it then inserts the script tag p inside the pixel h and again inserts the pixel h on the page body | |
| // this will essentially place the pixel on page, until now pixel was just being prepared | |
| var g = function() { | |
| if (e.body) { | |
| // place script inside pixel | |
| h.appendChild(p), | |
| // place pixel inside page body | |
| e.body.appendChild(h); | |
| // pick up the pixel(iframe) from the page | |
| var o = e.getElementById(m), | |
| // random string | |
| n = "s_" + d, | |
| // a function r which is executed when iframe is loaded | |
| r = function() { | |
| // after iframe is loaded, it runs some script from http://fqtag.com/pixel which might place some property called __sp on the global window object | |
| // it keeps checking the presence of this property on the page until is is present after some logic is run in the script loaded by pixel | |
| t.__sP && t.__sP[n] ? (t.__sP[n](o, y), o.onload = o.onreadystatechange = null) : setTimeout(r, 10) | |
| }; | |
| // call function r when iframe is loaded | |
| f(o, r) | |
| } else setTimeout(g, 0) | |
| }; | |
| //call function g | |
| g() | |
| } | |
| }(window, document); | |
| //this is again a self executing function which gets initialized and executed after the first one | |
| ! function() { | |
| // call the function FQTag, which was initialized in the above function with following object- | |
| // the values that you see in the form ${} are macros which are dynamically inserted on the server in this script | |
| // and their actual value would be different when the scrpit executes | |
| FQTag({ | |
| "org": "keswu4ug7detrumayur3", | |
| "s": "${AUCTION_ID}", | |
| "p": "${SELLER_MEMBER_ID}", | |
| "a": "${SITE_ID}", | |
| "cmp": "${CREATIVE_ID}", | |
| "fmt": "banner", | |
| "rd": "URL", | |
| "ctu": "CTURL", | |
| "ad": "ElementID", | |
| "rt": "display", | |
| "sl": "1", | |
| "fq": "1" | |
| }); | |
| }(); |
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