Update immutable object without breaking immutability in javascript

Question

If an object is Immutable in Javascript, how do I update its values and how do I get the updated value from its variable.

For example:

const todo = {
  text: 'Eat',
  completed: false
};

// To update todo completion to true
const updatedTodo = Object.assign({}, todo, { completed: true });

I can't reassign the new updatedTodo to Todo because I used const . If I change const to let and reassign it, doesn't that break immutability. I'm probably missing something.

Answer 1

todo is immutable but its properties aren't. You can change them either via Object.assign(todo, { completed: true}) (note how there's no empty object at the start, that way todo is actually modified), or you can simply set it via todo.completed = true .