how to checkbox checked or not in javascript code example

Example 1: How to check whether a checkbox is checked in jQuery?

//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
}

Example 2: check if checkbox is checked javascript

<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()" />