object.freeze.js

// Testing Object.freeze().

const list = { numbers: [1, 2, 3] };

console.log('adding 4 to the unfreezed list of numbers');

list.numbers.push(4);

console.log('unfreezed', list);

Object.freeze(list);

// Number added to the list [1, 2, 3, 4, 5].
console.log('adding 5 to the freezed list of numbers');
list.numbers.push(5);

// New property not added because of the freeze method.
console.log('adding letters to the freezed list');
list['letters'] = ['a', 'b', 'c'];

console.log('freezed', list);

const newList = Object.assign({}, list);

console.log('adding letters to the new cloned unfreezed list');
newList['letters'] = ['a', 'b', 'c'];

console.log('unfreezed', newList);

Object.freeze(newList['letters']);

// New property not added because of the freeze method. Error thrown.
console.log('adding d to the freezed list of letters');

try {
 newList.letters.push('d'); 
} catch (error) {
 console.log(error.message);
}

console.log('freezed', newList);