javascript - When to use the `#` symbol to get a DOM element?

Question

Sometimes I need to get elements like this:

var object = document.getElementById('ObjectName');

And sometimes like this:

var object = document.getElementById('#ObjectName');

What’s the difference between them?

Answer 1

No, you don't see

var object = document.getElementById('#ObjectName');

You don't see that because that would mean the id of the element starts with # and HTML4 id could only start "with a letter ([A-Za-z])".

What you see is sometimes people using the jQuery library in which the query language allows you to find an object using

var elem = $('#objectId');

And in the future you'll see more and more people using a similar query language with querySelector or querySelectorAll.