Justin Tadlock

JavaScript Logic is a plugin that allows you to add JavaScript however you want. There’s no need to add a script on all of your blog’s pages when you only need it on a few.
By using WordPress conditional tags or through a meta box on the Write Post/Page screen, you control what files are added to your site and when.

JavaScript Logic

Allows you to load JavaScript in a much more controlled way using WordPress conditional tags.

Frank Goossens

Optimizing Matters

EricJohnsonGuru

Eliminate Render-blocking Javascript in above-the-fold content with Async Javascript.
Render-blocking Javascript prevents above-the-fold content on your page from being rendered until the javascript has finished loading. This can impact on your page speed and ultimately your ranking within search engines. It can also impact your user’s experience.
Async JavaScript gives you full control of which scripts to add an ‘async’ or ‘defer’ attribute to or to exclude to help increase the performance of your WordPress website.

Async JavaScript

Plugin works as expected, settings are nice and minimal (using core styles) and there aren't any banners, notices or other marketing bloating things up.

Works great!

Async Javascript lets you add 'async' or 'defer' attribute to scripts to exclude to help increase the performance of your WordPress website.

JavaScript Logic vs Async JavaScript