Function getDefinedConstructorName

Implements a getter for the passed value's constructor-function name. In case of being able to retrieve a constructor, the remaining constraint is due to any function's name related property descriptor, which by default, hence without any intentional further change, is ...

{ ... writable: false, enumerable: false, configurable: true }
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...

• neither writable
• nor enumerable
• but configurable.

Thus, something like ...

Object.defineProperty(fct, 'name', { value: 'FOO' })
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... will change any passed function's name value to "FOO". As long as the latter can be safely excluded, the detection approach is safe. One even can or better yet should take advantage of it, branding a function permanently, in order to e.g. let constructor functions harden each their name as a countermeasure to code-minification tasks.