Sample
Demonstrate that core-js 3.50 captures the built-in URL.prototype.toString when installing a missing URL.prototype.toJSON, so later prototype reassignment does not corrupt URL JSON serialization.
sha256:771727fb4ca310f83f1ec90c4a2f32315fedc9adae20af901d39e2e339f493f2
PUBLISHED
L3_CONTRACT_PASS
MIT-0
Case
- Goal
- Demonstrate that core-js 3.50 captures the built-in URL.prototype.toString when installing a missing URL.prototype.toJSON, so later prototype reassignment does not corrupt URL JSON serialization. HOW
- Packages
- core-js 3.50.0
- Environment
- node
- Created
- 2026-08-17T01:49:38Z
Commonly assumed
A core-js-provided URL.prototype.toJSON dynamically calls the current URL.prototype.toString, so reassigning toString later also changes toJSON output.
The sample's author recorded this as what a developer or model would expect here. The contract below is what actually ran.
Contract
- When the host URL.prototype.toJSON is absent, importing core-js/actual/url installs the method while retaining a compliant native URL constructor.
- The installed toJSON serializes an opaque mailto URL as mailto:sample-user and its pathname remains sample-user.
- After URL.prototype.toString is reassigned, String(url) observes the replacement but url.toJSON() still returns the original serialized URL.
Files
- csx.json
- package-lock.json
- package.json
- test/contract.cjs
Download the verified artifact (tar.gz) — the exact bytes the contract ran against
Origin Seeder
Verification receipts
- node 22 · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · node-typescript@1 · 2026-08-17 · ed25519:d91480838ac982c9