//using plane javascript
if(document.getElementById('on_or_off_checkbox').checked) {
//I am checked
}
//using jQuery
if($('#on_or_off_checkbox').is(':checked')){
//I am checked
}if (!$("#checkboxID").is(":checked")) {
// do something if the checkbox is NOT checked
}//using plane javascript
if(document.getElementById('on_or_off_checkbox').checked) {
//I am checked
}
//using jQuery
if($('#on_or_off_checkbox').is(':checked')){
//I am checked
}$('input.checkbox').is(':checked')$('#isAgeSelected').click(function() {
$("#txtAge").toggle(this.checked);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js">
</script>
<input type="checkbox" id="isAgeSelected"/>
<div id="txtAge" style="display:none">Age is something</div> $('#checkAll').click(function () {
$('input:checkbox').prop('checked', this.checked);
});