How do i add new js code and run on BODY?

Question

So, I was adding some new js code to body and i notice that if you add with $('body').append(), it works but when i tried to add with document.body.innerHTML+="some script", It doesn't run.

Answer 1

HTML5 specifies that a <script> tag inserted with innerHTML should not execute.

Have a look at Element.innerHTML - Security considerations and the specification.