jQuery Grid Plugin - jqGrid

Hello Tony!

Now it seems to me I understand at the end the meaning of nd parameter in URL of GET requests. I found out, that IE8 use incorrect caching on ajax GET-requests. It sends no request to server, but gets the old data direct from the cache. If one loads the same data directly in IE8-GUI, it works without any problems. This problem is known und discussed in Internet. I found no other solution as switching off the caching for IE8. It can be done for example with respect of nd parameter

beforeRequest: function() {

    if ((!jQuery.browser.msie || (jQuery.browser.version !== “8.0″))

        && (typeof this.postData.nd !== 'undefined'))

        delete this.postData.nd;

}

Here I delete nd parameter from the send data for all browsers instead of Internet Explorer 8.0.

By the way, jquery.ajax function has an additional boolean parameter cache. Setting of cache to false follows to adding “_” parameter to the URL of GET-requests with the same way and meaning as nd parameter. In the code of ajax function from jquery-1.3.2.js one can find following fragment

if ( s.cache === false && type == “GET” ) {

      var ts = now();

      // try replacing _= if it is there

      var ret = s.url.replace(/(\\?|&)_=.*?(&|$)/, “$1_=” + ts + “$2″);

      // if nothing was replaced, add timestamp to the end

      s.url = ret + ((ret == s.url) ? (s.url.match(/\\?/) ? “&” : “?”)

+ “_=” + ts : “”);

}

where

function now(){

      return +new Date;

}

In my opinion the option named cache: false will be imediately correct understanded. For undestanding of nd paramerer on the other side, one sould undestend directly the implementation of switching the caching off.

Switching of the cache only for IE8 seems to me the best way as a default behavior.

Best regards

Oleg

Hello Mark

Thank you very much for your advice. I misunderstood meaning of some caching properties in HTTP header before. After you advice I read HTTP 1.1 RFC (14.9 from RFC 26156, http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9.3). I use now in my server response “Cache-Control: max-age=0“ in the HTTP header together with setting ETag.  And now everything works how I want: local browser cache will be used, but every new request contains “If-None-Match“ header with the value of ETag received with the first request. If the data are changed server send new data, but if the data stay unchanged, it reply with short response “HTTP/1.1 304 Not Modified” without any data and Browser get data from its local cache. Exactly what I want.

Now the setting of Internet Explorer: “Check for newer versions of stored pages” (found in Internet Options > General > Browser history > Settings) with standard “Automatically” setting works for my URLs exactly as the setting “Every time I visit the webpage”. I am happy!

Of cause, I stay have to use

beforeRequest: function() {

    if (typeof this.postData.nd !== “undefined”)

        delete this.postData.nd;

}

because usage an unique nd parameter added to every GET-request switch cache off.

So my suggestion to remove nd parameter from the list of default parameters of prmNames properties stays actually.

Tanks a lot

Oleg

Hello Tony!

At the end of the discussion I know what should be done on the server side for correct caching of GET results on the client side. No additional ajax option are required, at least to solve the problem.

The only problem what I see is using in jqGrid parameters in the form of objects like

jqGrid({

…

prmNames: {page:”page”,rows:”rows”, sort: “sidx”,order: “sord”, search:”_search”, nd:”nd”},…

})

Currently it is not possible to define shorter number of properties of prmNames. For successful caching I needs remove nd, for example. Creating a jqGrid with prmNames like

       {page:“page”,rows:“rows”, sort: “sidx”,order: “sord”, search:“_search”}

gives nor results, because it will be expanded to {page:”page”,rows:”rows”, sort: “sidx”,order: “sord”, search:”_search”, nd:”nd”} by p = $.extend(…) at the beginning of $.fn.jqGrid.

Usage

      beforeRequest: function() {if (this.postData.nd !== undefined) delete this.postData.nd;}

works, but is not nice.

So it seems to me the easiest way to allow remove some default values from prmNames would be to allow null values in prmNames.

If one change the code in “populate” function from

…

var prm = {}, dt, dstr;

prm[ts.p.prmNames.search] = ts.p.search; prm[ts.p.prmNames.nd] = new Date().getTime();

prm[ts.p.prmNames.rows]= ts.p.rowNum; prm[ts.p.prmNames.page]= ts.p.page;

prm[ts.p.prmNames.sort]= ts.p.sortname; prm[ts.p.prmNames.order]= ts.p.sortorder;

…

to something like

…

var prm = {}, dt, dstr;

if (ts.p.prmNames.search !== null) prm[ts.p.prmNames.search] = ts.p.search;

if (ts.p.prmNames.nd !== null) prm[ts.p.prmNames.nd] =new Date().getTime();

if (ts.p.prmNames.rows !== null) prm[ts.p.prmNames.rows]= ts.p.rowNum;

if (ts.p.prmNames.page !== null) prm[ts.p.prmNames.page]= ts.p.page;

if (ts.p.prmNames.sort !== null) prm[ts.p.prmNames.sort]= ts.p.sortname;

if (ts.p.prmNames.sort !== null) prm[ts.p.prmNames.order]= ts.p.sortorder;

…

than usage of

    prmNames: {page:”page”, rows:”rows”, sort: “sidx”, order: “sord”, search:”_search”, nd:null}

will solve all my problems without callback function beforeRequest.

If a table has all non-sortable columns one could use

    prmNames: {page:”page”, rows:”rows”, sort: null, order: null, search:”_search”, nd:null}

If the table need no data paging, then

    prmNames: {page:null, rows:null, sort: “sidx”, order: “sord”, search:”_search”, nd:null}

etc.

With this way one receives most flexibility and shortest URLs with minimum code changing.

What is your opinion about it?

Best regards,

Oleg

P.S. Thank you for your time. All my posts are too long, sorry.