onbeforeunload not always working

onbeforeunload not always working

I'm making a simple script to save some data on when a user access a page
and leaves a page, along with some other page details. The script "works",
but it doesn't work all the time. It seems to be working sporadically. I'm
not getting console errors on the time it doesn't. The server side works
fine.
window.onload = function() {
var timeStarted, i, c, l, timeLeft, pageData;
timeStarted = new Date().getTime();
i = <?php echo $model->id; ?>;
c = <?php echo $model->cat; ?>;
l= <?php echo $model->loc; ?>;
window.onbeforeunload = function(){
timeLeft = new Date().getTime();
pageData = [{name: 'timeStarted', value: timeStarted},
{name: 'i', value: job},
{name: 'c', value: cat},
{name: 'l', value: loc},
{name: 'timeLeft', value: timeLeft}];
// Set url for JavaSCript
var url = '<?php echo Yii::app()->createUrl("item/viewedItemInformation");
?>';
<?php echo CHtml::ajax(array(
'url'=>'js:url',
'data'=> "js: pageData",
'type'=>'post',
'dataType'=>'json',
)); ?>;
}
}
Note
I've just read this post window.onbeforeunload not working in chrome and I
am using chrome. However I seem to get the same results in FF too.
What is the correct away about solving this?