jsdom: instanceof Object fails?

Running a webapp inside JSDOM, I observe the following test failing:

let input: HTMLInputElement = ...; // got this from the DOM
let ok = input instanceof Object; // true in a browser, false in JSDOM

Does it make any sense?

I observe that the prototype chain of the “fake” HTMLInputElement goes to a fake Object and not the real Node one, but shouldn’t the Object in the code above also point to the same fake object?

To be clear: this code is running inside the webapp+JSDOM, not in the main Node code.

About this issue

Original URL
State: open
Created 7 years ago
Reactions: 2
Comments: 19 (7 by maintainers)

Most upvoted comments

This help?

copy the HTML*Element (etc.) types from the jsdom object and inject them into the global namespace before instanceof gets called. e.g. with mocha:

const { JSDOM } = require('jsdom')

const { instanceofCheck } = require('./instanceofCheck')
// const instanceofCheck = x => x instanceof window.HTMLElement

describe('JSDOM tests', () => {
    let jsDomInstance

    beforeEach(() => {
        jsDomInstance = new JSDOM()
        global.HTMLElement = jsDomInstance.window.HTMLElement
    })

    it('passes instanceof check', () => {
        expect(
            instanceofCheck(
                jsDomInstance.window.document.createElement('div')
            )
        ).toBe(true)
    })
})

bentorkington on Oct 17, 2022