A new, evolving set of ExtendScript scripts for simplifying work in Adobe Illustrator you don't find anywhere else!
You can install scripts first to have them listed as menu items in Illustrator, then to run them when you select them in the menu. For more check how to install the script in the Illustrator's Scripts menu.
For immediate executing the script, visit
File > Scripts > Other Scripts
in Illustrator, choose the downloaded script you want to run, and that's it!
Before it, select the paths you want to apply the script on. Otherwise all the existing paths of the artwork will be included.
It's possible to run scripts on each launch of Illustrator automatically (startup stripts).
Adobe Illustrator’s ExtendScript engine (based on an old version of JavaScript/ECMAScript) does not support default function parameters and other featues of the modern JavaScript. Take it into account when customizing scripts!
For more info check Adobe Illustrator Scripting Guide.