What are the three most common errors in JavaScript and when do they occur?
ReferenceError (variable does not exist or is in TDZ), TypeError (value is wrong type for the operation, like calling undefined or reading null.x), and SyntaxError (code is malformed and fails at parse time).
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More FAQs in JavaScript: not defined vs ReferenceError vs TypeError
ReferenceError is thrown when a variable does not exist or is in the TDZ. TypeError is thrown when a value is the wrong type for the operation, like calling a non-function or reading a property of null or undefined.
Because the var is hoisted with undefined, so the variable exists (no ReferenceError). But undefined() throws TypeError: x is not a function, because the value is not callable.
An error thrown during parsing, before any code runs. Malformed code like const x = ; causes it. The entire script or module does not execute when there is a SyntaxError.
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