Ask HN: Web Devs, What is this feature?

[mgpt]

Hey guys and gals

On any gitbooks (for example: https://codegangsta.gitbooks.io/building-web-apps-with-go/content/go_makes_things_simple/index.html). When you hover over a paragraph a little ' + ' icon comes up allowing yo to leave a comment on that specific paragraph

What is the feature called and is there a JS library or something for it?

Thanks in advance :)

[brudgers]

One way to investigate this would be using the developer tools in your browser. Usually the F12 key brings them up in the major browsers.

One of the great things about javascript and the web is that it is possible to 'dissassemble' most code at least partially.

Good luck.

[mgpt → brudgers]

Thanks