Question

How to seal and object to prevent adding new properties in JavaScript

Answer 1

const user = {
  id: 928737,
  name: 'Rose'
};

user.city = "new york";
console.log(user.city); 

Object.seal(user);
user.age = 42;
console.log(user.age); 



/*
run:
  
new york 
undefined
​   
*/

 

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Answer 2

const user = {
  id: 928737,
  name: 'Rose'
};

user.city = "new york";
console.log(user.city);


Object.preventExtensions(user);
Object.seal(user);
user.age = 48;
console.log(user.age); 


/*
run:
  
new york 
undefined
​   
*/

 

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