Fixing "Do not access Object.prototype method 'hasOwnProperty' from target object" error

Question

Based on hasOwnProperty() method docs I wrote the following:

const myObj = {
  prop1: 'val1',
  prop2: 'val2'
}

if (!myObj.hasOwnProperty('prop3')) {
  myObj.prop3 = 'val3'
}

But I'm getting this error:

Do not access Object.prototype method 'hasOwnProperty' from target object

Why does it not work if it's the same as in the docs, and how to fix it?

Raffo

Does this answer your question? How do I access the Object.prototype method in the following logic? – Ptolemaeus

Thanks :) Using Object.prototype.hasOwnProperty.call(obj, prop) did the job yes. But that doesn't explain why ESlint refuses a code copied straight from MDN docs – Raffo

ESLint can be configured in many ways and I'd be careful having the mindset that, "if it's in MDN docs, it's the only way to do it". Documentation can get stale or be opinionated. Take the info and do what's best for you and your project :D – Ptolemaeus

Sounds reasonable, thank you :) – Raffo

This answer explains why: https://mcmap.net/q/100204/-object-hasownproperty-yields-the-eslint-39-no-prototype-builtins-39-error-how-to-fix – Strikebound

Answer 1

Use the static Object.hasOwn() instead:

const myObj = {
  prop1: 'val1',
  prop2: 'val2'
}

if (!Object.hasOwn(myObj, 'prop3')) {
  myObj.prop3 = 'val3'
}

console.log(Object.keys(myObj)); //returns [ 'prop1', 'prop2', 'prop3' ]
console.log(myObj.prop3); //returns val3

Object.hasOwn() is intended as replacement for Object.prototype.hasOwnProperty() HasOwn

Aristaeus

hasOwn doesn't exist on type ... – Neutrino