Defering javascript - what is the correct html syntax defer or defer=“defer”

Question

What is the correct syntax for using the defer attribute in your javascript?

I have seen it done two ways:

1:

Answer 1

The async and defer attributes are boolean attributes that indicate how the script should be executed. The defer and async attributes must not be specified if the src attribute is not present.

https://www.w3.org/TR/html5/scripting-1.html#attr-script-defer