stampit API
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Enables obj instanceof MyStamp in ES6 environments
const InstanceOf = require('@stamp/instanceof');
// or
import InstanceOf from '@stamp/instanceof';
It uses the well known Symbol hasInstance to test instance.


Create a stamp:
let MyStamp = compose({
properties: { ... },
initializers: [function () { ... }]
The following doesn't work:
const obj = MyStamp();
obj instanceof MyStamp === false;
Compose the InstanceOf to your stamp:
MyStamp = MyStamp.compose(InstanceOf);
Now it works:
const myObject = MyStamp();
obj instanceof MyStamp === true;


  • We do not recommend to use instanceof in JavaScript in general.