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  • Ahmed Elgendy thinks this is interesting:

One thing that often misleads people learning closures is that they think the environment in the closure must have a copy of all the variables and their values. It doesn’t. In fact, the environment references the live variables being used by your code, so if a value is changed by code outside your closure function, that new value is seen by your closure function when it is evaluated.

From

Cover of Head First JavaScript Programming

Note

A warning about closures?