Question

[NUMERIC4]

https://github.com/Asabeneh/30-Days-Of-JavaScript/blame/55d8e3dbc0410d64c1dc3ea5915e015a7950cf2a/12_Day_Regular_expressions/12_day_regular_expressions.md#L380

Firstly thanks for this project. It was really helpfull to catch things up.
In this line there are two \ exist one of them belongs to b but other one is meaningful or not?
when i typed it in js compiler i got an error when i change that line with " const pattern = /\b\w{4}\b/g " it works as expected