Object Descriptors & Property Flags

What are the object mutability test results?

const extensible = { a: 1 };
const sealed = Object.seal({ b: 2 });
const frozen = Object.freeze({ c: 3 });

console.log(
  Object.isExtensible(extensible),
  Object.isSealed(sealed),
  Object.isFrozen(frozen),
  Object.isExtensible(frozen)
);

true, true, true, true
true, true, true, false
The console will log 'true, true, true, false' because: 1) A normal object is extensible by default (true), 2) A sealed object passes the isSealed test (true), 3) A frozen object passes the isFrozen test (true), 4) A frozen object is not extensible (false) - freezing implicitly prevents extensions, 5) These testing methods provide a way to check object mutability status, 6) They're useful for conditional logic that depends on object mutability, 7) Understanding these relationships is key to working with object immutability in JavaScript.
false, false, false, false
true, false, true, false

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