js_seal.js

var sealedObject = {
    value1 : 1,
    value2 : 2
};
 
Object.seal(sealedObject);
console.log(Object.isSealed(sealedObject)); // true
 
// 삭제 불가
delete sealedObject.value1;
console.log(sealedObject.value1); // 1
 
// 변경 가능
sealedObject.value2 = 3;
console.log(sealedObject.value2); // 3
 
// 객체 추가 불가
sealedObject.value3 = 3;
console.log(sealedObject.value3); // undefined