Passing in NULL as a parameter in ES6 does not use the default parameter when one is provided

Question

Is there a known reason why passing in null as a parameter in ES6 does not use the default parameter when one is provided?

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Answer 1

That's just how default parameters are defined in the spec. See MDN: (emphasis mine)

Default function parameters allow formal parameters to be initialized with default values if no value or undefined is passed.

null is neither no value, nor undefined, so it doesn't trigger the default initialization.