Performance regression in isPlainObject utility

[benelliott]

🐛 Bug Report

The changes to isPlainObject introduced in #767 added a more comprehensive check that worked for objects across iframes which relies on Function.toString:

	const Ctor =
		Object.hasOwnProperty.call(proto, "constructor") && proto.constructor
	return (
		typeof Ctor == "function" &&
		Function.toString.call(Ctor) === objectCtorString
	)

This more robust check is quite expensive for the common case where the object instance comes from the same frame and a simpler equality check would suffice.

I will submit a PR to remedy this.

Link to repro

N/A (Perf)

To Reproduce

N/A (Perf)

Observed behavior

In our app we invoke immer.applyPatches multiple times per second based on WebSocket events. The calls to Function.toString have a noticeable performance impact on our app.

Expected behavior

The utility method should not have a substantial impact on performance.

Environment

We only accept bug reports against the latest Immer version.

• Immer version:
• I filed this report against the latest version of Immer
• Occurs with setUseProxies(true)
• Occurs with setUseProxies(false) (ES5 only)

[mweststrate]

🎉 This issue has been resolved in version 9.0.3 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀