checkbox checked if condition javascript

if (document.getElementById('id of the check box here').checked) {
	// it is checked. Do something
} else {
	// it isn't checked. Do something else
}

if ($('input[name="transport"]').is(':checked')) {
	alert('checked');
	alert($(this).attr('id')); //To get ID of checkBox
}<input type="checkbox" onchange="doSomething(this)">

function doSomething(element){
   var isChecked=element.checked;
	//do some action if it is checked
}