How does Object.assign() treat null or undefined sources?

Object.assign() ignores null or undefined sources.

When Object.assign() is called with null or undefined as one of the source objects, it simply ignores them and does not throw an error. This means that only the properties from valid objects are copied to the target object, and any null or undefined sources are skipped.

const target = { a: 1 };
const source = null;
const result = Object.assign(target, source);
console.log(result); // { a: 1 }