What does the regular expression \|(?=\w=>) mean?

Question

I am an amateur in JavaScript. I saw this other (now deleted) question, and it made me wonder. Can you tell me what does the below regular expression exactly mean?

split(/\|(?=\w=>)/)

Does it split the string with |?

Answer 1

The regular expression is contained in the slashes. It means

\|        # A pipe symbol. It needs to be scaped with a backslash
          # because otherwise it means "OR"
(?=       # a so-called lookahead group. It checks if its contents match 
          # at the current position without actually advancing in the string
   \w=>   # a word character (a-z, A-Z, 0-9, _) followed by =>
)         # end of lookahead group.

Answer 2

It splits the string on | but only if its followed by a char in [a-zA-Z0-9_] and =>

Example:

It will split a|b=> on the |

It will not split a|b on the |