🔰property testing

• JS ⟩ value ⟩ object ⟩ property ⟩ testing properties

check whether an object has a property.

'prop' in obj                     // in operator
Object.hasOwn(obj, 'prop')        // recommended
obj.hasOwnProperty('prop')        // not recommended
obj.propertyIsEnumerable('prop')

⭐ the following methods/operators all support String / Symbol keys.

method/operator	own enum	own nonenum	inherited enum	inherited nonenum
in	✅	✅	✅	✅
.hasOwn()	✅	✅
.hasOwnProperty()	✅	✅
.propertyIsEnumerable()	✅

⭐️

Every property in JavaScript objects can be classified by 3 factors:

• String / Symbol

• enumerable / non-enumerable

• own / inherited (from the prototype chain)

📘 MSN

🔴

👥

📗

📘