####### Don't go crazy
Tumblr allows u to like 1000 pics a day. (so keep a track by watching console.log on chrome or just count it)
####### How To
Either copy paste script as it is into your developer console or install this extension https://chrome.google.com/webstore/detail/custom-javascript-for-web/poakhlngfciodnhlhhgnaaelnpjljija and paste the code for tumblr.