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Javascript page rendering speed test script sharing

Source: Internet
Author: User
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Copy codeThe Code is as follows:/* Get the start timestamp of rendering and save it in the array PAGE_SPEED_TIME */
<Html> <script type = "text/javascript">/* tag */PAGE_SPEED_TIME = [new Date (). getTime ()]; </script> ......
</Head>

Copy codeThe Code is as follows:
......
/* Calculate the time consumed for page loading at the end of the page */
</Body>
<Script src = "http://ossweb-img.qq.com/images/js/pagespeed/page_speed_v2.js"> </script>


Next we will analyze the content of the page_speed_v2.js file. Reformat the script for easier reading.
Copy codeThe Code is as follows:
/* Execute the anonymous function build object PageSpeed */
; (Function (){
PageSpeed = {};/* There is no var keyword here, which is equivalent to referencing window. PageSpeed */

/**
* Bind the createScript Method
*
* @ Param String a script tag's src attribute value
* @ Param String B the id attribute value of the script tag
*/
PageSpeed. createScript = function (a, B ){
Var c = null;

If (document. getElementById (B) {/* the script tag already exists */
C = document. getElementById (B)
} Else {/* does not exist. Create a script tag */
C = document. createElement ('script ');
Var d = null;
If (document. getElementsByTagName ){
D = document. getElementsByTagName ('head') [0] | document.doc umentElement;
} Else {
D = document.doc umentElement;
}
D. insertBefore (c, d. firstChild);/* call the insertBefore method to insert the newly created script tag as the first child element */
}

/* The curly braces show the code snippet grouping function */
{
C. setAttribute ('type', 'text/html ');
C. setAttribute ('style', 'display: none ;');
C. setAttribute ('charset', 'gb2312 ');
C. setAttribute ('id', B );
C. setAttribute ('src', );
}

Return c;/* return the successfully created script Tag Element */
};

/**
* Bind the submitDataForPageSpeed Method
*
* @ Param Object a Map Object
*/
PageSpeed. submitDataForPageSpeed = function (){
Var B = {
'Name ':'',
'Rate': 0
};
B. name = a. name;
B. rate = a. rate;

/* The last element of a. PAGE_SPEED_TIME array minus the first element */
B ['1'] = a. PAGE_SPEED_TIME [a. PAGE_SPEED_TIME.length-1]-a. PAGE_SPEED_TIME [0];

For (var I = 1; I <a. PAGE_SPEED_TIME.length-1; I ++ ){
B [(I + 1) + ''] = a. PAGE_SPEED_TIME [I]-a. PAGE_SPEED_TIME [0]
}

/* Target script for submitting the speed test result */
Var c = 'HTTP: // pagespeed-ied.qq.com/r.cgi ';

/* Traverse the elements of array B and construct a query string */
Var d = [];
For (var p in B ){
D. push (p + '=' + B [p])
}
C + = '? '+ D. join ('&');

/* Create a script tag and submit the speed test result */
PageSpeed. createScript (c, 'submitforpagespeed ')
};

/**
* Bind the defaultSubmit Method
*
*/
PageSpeed. defaultSubmit = function (){
Var a = '';
Try {
A = location. host
} Catch (e ){}

Var B = {
'Name':,
'Rate': 1,
'Page _ SPEED_TIME ': []
};

If (! B. name ){
Return
}

If (! (Typeof (PAGE_SPEED_TIME) = 'object' & PAGE_SPEED_TIME instanceof Array )){
Return
}

/* Get the new timestamp */
PAGE_SPEED_TIME.push (new Date (). getTime ());

B. PAGE_SPEED_TIME = PAGE_SPEED_TIME;

/*
* I don't understand why I need a new variable aaa. Can I use a directly?
* The try... catch structure uses a new variable aaaa, but it is never used later. Why? Should it be aaa?
*/
Var aaa = '';
Try {
Aaaa = location. host
} Catch (e ){}

Var c = Math. floor (Math. random () * 10000 );

If (aaa = "ktv.qq.com" | aaa = "ttd.qq.com" | aaa = "tian.qq.com" | aaa = "sura.qq.com" | aaa = "gw.tnt.qq.com" | aaa = "007.qq.com ") {
C = Math. floor (Math. random () * 1000 );
}

/* Submit data with random probability */
If (c <= B. rate * 1 ){
PageSpeed. submitDataForPageSpeed (B );
}
};

/**
* Bind the submit method (for CDN speed measurement ?)
*
* @ Param String a name
*/
PageSpeed. submit = function (){
Var B = PageSpeed. cdn_page_speed_submitData;
Var c = {};
For (var p in B ){
C [p] = B [p]
}
C. name = a | c. name;
PageSpeed. submitDataForPageSpeed (c );
}
})();

Try {
/* Try to submit data in 1 second */
SetTimeout (function (){
PageSpeed. defaultSubmit ()
},
1000 );
} Catch (e ){}

/* For the last comment, the second part is a 32-bit hexadecimal number, which should be similar to the ETag used to mark the content version */
/* | XGv00 | ca82276cd78ac911d3d4310ba1408236 */

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