.js in a custom theme (1.7)

[pedrobrochero]

Greetings,I'm developing a theme and cannot make my slider work. (works perfectly on html). Cannot import the js files:

 

 

Custom function on js works perfectly if I add it to theme.js, but if copy-paste the content of "slick.js", webpack gives an error 

 

 

I tried to include the file copying in assets/js folder, and adding it on theme.yml, without success. 

 

 

Thanks in advance who anyone could help me.