delete is “dog slow”. When you use
with, V8 has to wait until run time to resolve the scope chain. When you use
delete V8 has to transform your object from a highly-optimized class structure into a slower hash table.
Lars and Kasper mentioned that
So never use
delete in a production application!
AJ O’Neal quotes Douglas Crockford saying that removing
delete is about from 13:33 through 16:50.