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JS
JavaScript error

TypeError

The JavaScript exception "calling a builtin X constructor without new is forbidden" occurs when you try to call a builtin constructor without using the new keyword. All modern constructors, such as Promise and Map, must be called with new.

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

The error messages

TypeError: Constructor X requires 'new' (V8-based)
As listed by MDN Web Docs
TypeError: Promise constructor cannot be invoked without 'new' (V8-based)
As listed by MDN Web Docs
TypeError: calling a builtin X constructor without new is forbidden (Firefox)
As listed by MDN Web Docs
TypeError: calling X constructor without new is invalid (Safari)
As listed by MDN Web Docs

Details

Category
TypeError
Severity
error
Runtime
both

Related errors

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Source: MDN Web Docs. Data fetched 2026-09-25T01:48:37.273Z.