What is the difference between the 'in' operator and the 'hasOwnProperty' method?

The in operator and the hasOwnProperty method in JavaScript are used to check for the presence of a property in an object, but they work differently:

• in checks whether a property with the specified name exists in the object or in its prototype chain.

• hasOwnProperty checks whether a property exists directly on the object itself, without considering prototypes.

Example:

const obj = { a: 1 };
console.log('a' in obj); // true
console.log(obj.hasOwnProperty('a')); // true

console.log('toString' in obj); // true, because toString is in the Object prototype
console.log(obj.hasOwnProperty('toString')); // false

Thus, if you need to check whether a property belongs directly to the object itself and is not inherited, use hasOwnProperty. If it's enough to check for the presence of a property anywhere in the chain, use in.