When is a lexical environment created in JavaScript?
Every time the engine enters a new scope: once for the global scope, on each function call, and for each block (pair of braces) containing let or const declarations.
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More FAQs in Lexical Environment in JavaScript Explained
An internal data structure that manages scope. It consists of an environment record (the variable bindings) and a reference to the outer (parent) lexical environment. The engine creates one for each scope.
It means the outer environment reference is determined by where the code is written in the source, not where the function is called. This is why JavaScript is called lexically (statically) scoped.
In the spec, the variable environment holds var and function declarations, while the lexical environment holds let and const. In practice they are often the same object, but the distinction matters in edge cases like catch blocks.
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