JavaScript Instanceof Guide
instanceof checks if an object has a specific constructor in its prototype chain. The guide walks through instanceof Usage. `obj instanceof Constructor` — true if Constructor.prototype is in obj's prototype chain. `[] instanceof Array` — true. `[] instanceof Object` — true (Array extends Object). `"str" instanceof String` — false (primitives). Override: Symbol.hasInstance customizes instanceof behavior. The guide is organized into 1 sections that build on each other, each pairing a prose explanation with runnable code. Related guides: Arrays, Strings, Numbers, Math, Date. This is one of 145 JavaScript guides on JS Reference — see the full list on the guides page. Practice what you learn in the JavaScript playground, and look up any unfamiliar term in the JavaScript glossary.