Uncaught TypeError: Cannot assign to read only property

Question

I was trying out this really simple example from the awesome \"Professional JavaScript for Web Developers\" book by Nicholas Zakas but I can\'t figure what I am doing wrong

Answer 1

When you use Object.defineProperties, by default writable is set to false, so _year and edition are actually read only properties.

Explicitly set them to writable: true:

_year: {
    value: 2004,
    writable: true
},

edition: {
    value: 1,
    writable: true
},

Check out MDN for this method.

writable
true if and only if the value associated with the property may be changed with an assignment operator.
Defaults to false.