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conformance · v134

v134 · error-iserror — conformance probe

6 assertions drawn from the spec. Each is a single contract the spec text makes. Pass/fail reflects what this browser executed; blocked means the contract was not run because it needs user mediation, hardware, or another unavailable precondition. Open the page in Chrome stable / canary / Firefox / Safari to compare.

browser: spec: https://tc39.es/proposal-is-error/ chromestatus: #5847855083028480 generated 2026-06-01T08:30:00Z by conformance-author-v1-subagent
0
pass
0
fail
0
blocked
6
total
id contract kind verdict detail
error-iserror-is-function Error.isError is a function (the proposal adds a static method to Error). typeof
error-iserror-true-for-error-instance Error.isError(new Error()) returns true. script
error-iserror-true-for-typeerror Error.isError detects subclassed builtins (TypeError, RangeError, etc.). script
error-iserror-false-for-plain-object A plain object that looks like an error ({ message, stack }) is not an error. script
error-iserror-false-for-non-errors Primitives and other built-ins return false. script
error-iserror-cross-realm Error.isError detects Error instances from a different realm (e.g. an <iframe>'s window). script