Question

i don’t really understand why the author in the “Javascript & Jquery: the missing manual , second edition” advise the sentence below:

When adding the src attribute to link to an external JavaScript file, don’t add any JavaScript code
between the opening and closing tags. If you want to link to an external JavaScript file and add
custom JavaScript code to a page, use a second set of tags. For example:

what is the advantage of using the second script tag instead of only using one?

Answer 1

Because, when there is a src attribute, the content of the element will be ignored.

From the specification:

The script may be defined within the contents of the SCRIPT element or in an external file. If the src attribute is not set, user agents must interpret the contents of the element as the script. If the src has a URI value, user agents must ignore the element’s contents and retrieve the script via the URI.