Object.seal() vs Object.freeze() in JavaScript

Both methods allow you to control the mutability of objects, but they have different behaviors.

1-Object.seal(obj):

This method seals an object, which means that you can’t add or delete properties, but you can still modify the values of existing properties.

let obj = {
a: "a",
b: "b",
};
Object.seal(obj);
obj.a = 2; //allowed
delete obj.b; //Not allowed
obj.c = "c"; //Not allowed
console.log(obj); // {a: 2, b: "b"};

2-Object.freeze(obj):

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This method freezes an object, which means that you can’t add, delete or modify the values of existing properties. This method makes completely read-only objects.

let obj2 = {
a: "a",
b: "b",
};
Object.freeze(obj2);
obj2.a = 2; //Not Allowed
delete obj2.b; //Not Allowed
obj2.c = "c"; //Not Allowed
console.log(obj2); // {a: "a", b: "b"}; //remains same

3-Object.preventExtensions(obj):

This method prevents objects from extensions, which means you can’t add properties to the object, but you can add and delete the object's existing properties.

let obj3 = {
a: "a",
b: "b",
};
Object.preventExtensions(obj3);
obj3.a = 2; //Allowed
delete obj3.b; //Allowed
obj3.c = "c"; //Not Allowed
console.log(obj3); // { a: 2 }//modified object

Summary: