Why am I getting undefined if I remove 'this' ?

Question

Inside Snake constructor, I have called Animal constructor. But if I remove the this keyword I am getting undefined in the output. WHY ??

https://code.sololearn.com/c3xDtSPIndz0/?ref=app

Answer 1

Levi as you pointed out "this" is a keyword
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/this