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 here  Must be something really simple that I missed but I m stuck   Here is the code    use strict    var book        Object defineProperties book        originYear            value  2004          writable  false              year            value  2004             edition            value  1             year             get  function                 return this  year                      set  function newValue                if newValue  gt  this originYear                    this  year   newValue                  this edition    newValue - this originYear                                     console log book edition   book year   2006  console log book edition     The error I am getting on the Chrome console is   Uncaught TypeError  Cannot assign to read only property   year  of  main js 31 Object defineProperties year setmain js 39  anonymous function   Can someone please explain where I have gone wrong   Here is the fiddle

User · Answer

I tried changing year to a different term  and it worked   public methods         get  function             return this  year              set  function newValue            if newValue  gt  this originYear                this  year   newValue              this edition    newValue - this originYear

User · Answer

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

User · Answer

If sometimes a link  will not work  so create a temporary object and take all values from the writable object then change the value and assign it to the writable object  it should perfectly  var globalObject         name  quot a quot       age 20   function         let localObject         name  a       age 21           this globalObject   localObject

[javascript] Uncaught TypeError: Cannot assign to read only property

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