check if checkbox is checked javascript

//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
}

var checkBox = document.getElementById(id_field);
			if (checkBox.checked== true){
            }

if(document.getElementById('on_or_off_checkbox').checked) {
    //I am checked
}else{
	//I am not checked
}

document.getElementById("checkbox").checked;

<input type="checkbox" onchange="doSomething(this)">

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

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
}

        
            
        
     const cb = document.getElementById('accept');
console.log(cb.checked);

<script type=text/javascript>
  function validate(){
    if (remember.checked == 1){
      alert("checked") ;
    } else {
      alert("You didn't check it! Let me check it for you.")
    }
  }
</script>

<input id="remember" name="remember" type="checkbox" onclick="validate()" />