Object.freeze(), seal(), preventExtensions()

• Object.freeze() makes an object immutable: cannot add, delete, or change properties.

• Object.seal() prevents adding or deleting properties, but existing properties can be changed.

• Object.preventExtensions() prevents adding new properties, but existing ones can be changed or deleted.

const obj = { a: 1 };
Object.freeze(obj);
obj.a = 2; // ignored or error
console.log(obj.a); // 1