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JS
JavaScript error

SyntaxError

The JavaScript exception "invalid assignment left-hand side" occurs when there was an unexpected assignment somewhere. It may be triggered when a single = sign was used instead of == or ===.

Reference entryJavaScriptFetched
This is a reference entry from MDN Web Docs. A full explanation with fixes has not been written yet.

The error messages

SyntaxError: Invalid left-hand side in assignment (V8-based)
As listed by MDN Web Docs
SyntaxError: invalid assignment left-hand side (Firefox)
As listed by MDN Web Docs
SyntaxError: Left side of assignment is not a reference. (Safari)
As listed by MDN Web Docs
ReferenceError: Invalid left-hand side in assignment (V8-based)
As listed by MDN Web Docs
ReferenceError: cannot assign to function call (Firefox)
As listed by MDN Web Docs
ReferenceError: Left side of assignment is not a reference. (Safari)
As listed by MDN Web Docs

Details

Category
SyntaxError or ReferenceError, depending on the syntax
Severity
error
Runtime
both

Related errors

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Source: MDN Web Docs. Data fetched 2026-09-25T01:48:37.274Z.