@wbotelhos This issue comes from this line :
star = this.stars[Math.ceil(score) - 1];

When the option 'half' is true and the cursor is before the first star it looks for a negative index in the array. It can be easly fixed with :
star = this.stars[Math.max( Math.ceil(score) - 1,0)];

The problem exist and without cancel enabled. What I need to change with this line star = this.stars[Math.max( Math.ceil(score) - 1,0)]; ? This was the solution for me: https://github.com/mbrainiac/raty/commit/958b92dcabcbc342a041e4073f6c0e216f36ac45

It can be reproduced very easly :
Go to : https://wbotelhos.com/raty
Go to the example for "Half" and try to select 0 star ( put the cursor before any star ) in the console you will see errors adding up.

The problem exist and without cancel enabled. What I need to change with this line star = this.stars[Math.max( Math.ceil(score) - 1,0)]; ? This was the solution for me: https://github.com/mbrainiac/raty/commit/958b92dcabcbc342a041e4073f6c0e216f36ac45

it should also in this section _setTitle:function() change the line star = this.stars[Math.max( integer - 1,0)]