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Knockout & jQuery takes a VERY long time using push...

Posted on 2014-11-28
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Last Modified: 2014-12-02
Hi all,

I am using jQuery and Knockout on my webapp, but when I try to process an array (~400 elements) the request can take a very long time to execute (around 60s!)

JS
AppViewModel.page_model = {
    my_log_entries : ko.observableArray(),
    };

function AjaxReportsMyLog()
{
	var myCommand = [];
	myCommand.cmd = "GetReportMyLog";
	var params = JSON.stringify({LoginName:AppViewModel.user_session.UserDetails.LoginName, SessionID:AppViewModel.user_session.UserDetails.SessionID });
	myCommand.data = params;
	myCommand.onSuccess = function(o)
	{
		AppViewModel.page_model.last_updated(new Date().toLocaleString());
		if(JSON.stringify(AppViewModel.page_model.my_log_entries()) != JSON.stringify(o.ajaxdata.ListOfEntries))
		{
			alert('Starts here...');
			$.each(o.ajaxdata.ListOfEntries, function(key, val)
			{
				AppViewModel.page_model.my_log_entries.push(val);
			});
			alert('60s later, gets here!!');
		}
	}
	myCommand.onError = function(o)
	{
		Utils.Dialog_Server_Error(o.errorThrown);
	}
	Api.Exe(myCommand);
};	

$(document).ready(function()
{
	. . 
	. . 
    AppViewModel.page_model.my_log_entries.removeAll();
	AjaxReportsMyLog();
});

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html
<script type="text/html" id="my-log-template">
	<table class="report">
		<tr>
			<th class="mv-log2">Field 1</th>
			<th class="mv-log4">Field 2</th>
			<th class="my-log3">Field 3</th>
		</tr>
		<tbody id="my-log-records" data-bind="foreach: $data">
			<tr class="section">
				<td data-bind="text: $data.Field1"></td>
				<td data-bind="text: $data.Field2"></td>
				<td data-bind="text: $data.Field3"></td>
			</tr>
		</tbody>
	</table>
</script>

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It all seems to work just fine, just takes a very long time!!!

Any help would be appreciated
0
Comment
Question by:jatkin
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6 Comments
 
LVL 43

Expert Comment

by:Rob
ID: 40470873
Might be a silly question but you have called the applyBindings method?
i.e. "ko.applyBindings(AppViewModel.page_model);" ?
0
 
LVL 43

Expert Comment

by:Rob
ID: 40470876
Also you've encapsulated your table in a <script> tag? why?  that's not necessary.
0
 
LVL 43

Expert Comment

by:Rob
ID: 40470897
I've set up a demo here: http://jsbin.com/remeyi/1/edit?html,js,output

I've had to change some code and add a call to some dummy data (over 400 records: http://jsbin.com/futoze/1.json) .  This runs in about a couple of seconds.  Is there anything more complicated to your actual data than what you see here?
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LVL 4

Author Comment

by:jatkin
ID: 40473442
Hi,
Thanks for the suggestions...
I had applied the bindings.
The SCRIPT tag was inherited from the previous developer :-) It appears that as this form was previously used for multiple reports, they used the ID of the SCRIPT to run the appropriate section. Not needed anymore now so I'll remove it.
I do believe however that I have identified the issue... well, I have fixed the delay anyway...
As the "AppViewModel.page_model.my_log_entries" is an observable object, each time an entry is added to it, it is reevaluated. Looks like this takes some time in an array this time (quite why it is 60s I don't know!)
However, I have applied the 'pausable' extension to knockout:
https://github.com/Areson/Knockout-Extensions/wiki/Knockout.Pausable
and it seems to be resolved. Now takes a fraction of a second to process:

AppViewModel.page_model.my_log_entries.pause();
$.each(o.ajaxdata.ListOfEntries, function (key, val)
{
    AppViewModel.page_model.my_log_entries.push(val);
});
AppViewModel.page_model.my_log_entries.resume();

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0
 
LVL 43

Accepted Solution

by:
Rob earned 500 total points
ID: 40474356
Yes, that does make sense.  Great to hear it's working for you.  

Going forward, If you don't want to use a plugin, you could just write the values to a temporary array, which is what I do anyway.

e.g.
var temp = []; // empty array
$.each(o.ajaxdata.ListOfEntries, function (key, val)
{
    temp.push(val);
});

AppViewModel.page_model.my_log_entries(temp);

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Now the my_log_entries observable is only being updated once
0
 
LVL 4

Author Closing Comment

by:jatkin
ID: 40475461
This looks like a much neater way that pausing the observable!
Thanks a lot for the help.
James
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