JavaScript Array Join Comma Default Separator

When you join an array in JavaScript, the default separator is a comma:

node> ['j', 'a', 'k', 'e'].join()
'j,a,k,e'

In production code, you often want to pass an empty string instead.

node> ['j', 'a', 'k', 'e'].join('')
'jake'

This is something I relearn from time to time, because it works differently in Ruby.

irb> ["j", "a", "k", "e"].join()
=> "jake"

MDN Array Join Docs