ReferenceError
Thrown when code refers to a binding that doesn't exist — the code was valid JavaScript, but the name it looked for wasn't there when it ran.
new ReferenceError(message)
Purpose
A ReferenceError means the engine tried to look up a binding (a variable, function, or class
name) and found nothing by that name in scope. Unlike a SyntaxError, the file was valid
JavaScript and had already started running — the problem only appears once that specific line
executes.
Example
console.log(greting); // typo for "greeting"Uncaught ReferenceError: greting is not definedCommon causes
- A typo in a variable or function name.
- Using a variable before its
let/constdeclaration runs — the “temporal dead zone” — even though the declaration exists later in the same scope. - Forgetting to import something that’s defined in another module.
- Referring to a variable outside the block or function where it was declared with
letorconst.
Distinguishing it from other errors
A ReferenceError means the name doesn’t exist. Compare with TypeError, which means the name
exists and holds a value, but that value doesn’t support the operation attempted on it (for
example, calling something that isn’t a function). If nothing ran at all — not even code before the
failing line — the problem is a SyntaxError instead.
Runtime notes
ReferenceError is part of ECMAScript, so the error type and the temporal-dead-zone behavior are
identical across browsers and Node; only the exact message wording is engine-specific.