How can i make my checkbox show a hidden span if it is checked

Question

this is my checkbox

<?php  $create = array(
           'name'=> 'single_obs_value',
           'id' => 'Heart_Rate',
           'class' => 'singleobs',
           'value' => $cp->odvalue_list_id,
           'checked' => sel_checkbox($singleobsnormal['single_obs_value'] == $cp->odvalue_list_id),
           'style'=> 'float: left; margin-right: 10px;'
       );
?>

When my checkbox is ticked it shows a hidden span and when unticked it hides the span. I have done this using javascript.

$('#Heart_Rate').on("change", function() {  

    if (this.checked) {

         $('#hrsObs').fadeIn('fast');

    } else {

        $('#hrsObs').fadeOut('fast');
    }
}   

This function works perfectly for if i am checking or unchecking the box. But when the page loads i need a function to check if the checkbox was checked or not and thus hide or show the span which has been given a class of #hrsObs. Any suggestions?

Answer 1

$('#Heart_Rate').attr('checked') // give you you the information

Answer 2

You can use this in DOM ready event:

$(document).ready(function(){
 if($('#Heart_Rate:checked').length){
   $('#hrsObs').fadeIn('fast');
}});

Answer 3

Give this a try:

jQuery(document).ready(function(){ 

        //cache these since you'll be using them a few times
        var $heartRate  = $('#Heart_Rate'),
            $hrsObs     = $('#hrsObs');

            $heartRate.on("change", isChecked());

            function isChecked(){
                if($heartRate.prop("checked")){
                    $hrsObs.fadeIn('fast');
                }
                else{
                    $hrsObs.fadeOut('fast');
                }
            }

            //run function now that page has loaded
            isChecked();

    });