document.onclick = function(){
alert('dom');
}

<script src="jquery-3.1.0.js"></script> 
<script>
console.log(jQuery(document));//[document]
console.log($(document));//[document]
console.log(document);//#document
</script>

<script src="jquery-3.1.0.js"></script> 
<script>
//无反应
$(document).onclick = function(){
alert(0);
};
//Uncaught TypeError: document.click is not a function
document.click(function(){
alert(1);
});
</script>

console.log(document === $(document)[0]);//true
console.log(document === $(document).get(0));//true

//先弹出0，再弹出1
document.onclick = function(){
alert(0);
}
$(document).click(function(){
alert(1);
});