For compressing strings, just a little bit, when you already know good keywords to use for the compression. I use it to trim cookies.

minicomp.js

 var compList = ['products', 'collections', '_thumb.jpg', '.myshopify.com/', '//cdn.shopify.com/s/files/', 'http://', 'shopify.com'];
 
 function miniComp(str) {
   for(var i=0; i<compList.length; i++) {
     str = str.split(compList[i]).join('#['+i+']'); //Split/join vs regex speed = surprising
   }
   return str;
 }
 
 function miniDecomp(str) {
   for(var i=0; i<compList.length; i++) {
     str = str.split('#['+i+']').join(compList[i]);
   }
   return str;
 }