JQuery id 있는지 확인

by JM note

HTML

<script src='//rawgit.com/eu81273/jsfiddle-console/master/console.js'></script>
<script src="//code.jquery.com/jquery.min.js"></script>

<div id='box1'></div>

<script>
var box1_exist = $("#box1").length ? true : false;
var box2_exist = $("#box2").length ? true : false;
console.log( box1_exist );
console.log( box2_exist );
</script>