Javascript - error:Cannot set property author of #<xxx> which has only a getter. But if I change the getter function name, this error disappears

MiraLing
June 23, 2023
294 views
0 votes
2 Answers

When the class has only one getter and no setter, it will report an error, but if I change the name of the getter, the error will disappear.

The code that will report an error:

class Book {
  constructor(author) {
    this.author = author;
  }
  // getter
  get author() {
    return this.author;
  }

}
const novel = new Book('anonymous'); 
console.log(novel.author);
//TypeError: Cannot set property author of #<Book> which has only a getter

Code that will not report an error:

class Book {
  constructor(author) {
    this.author = author;
  }
  // getter
  get writer() {        //just change the name
    return this.author;
  }

}
const novel = new Book('anonymous');
console.log(novel.writer);
//anonymous

update：

Why doesn’t this code report an error saying that there is only a getter and no setter?

class Book {
  constructor(name) {
    this._author = name;
  }
  // getter
  get author() {
    return this._author;
  }
}

let a = new Book("Mike")
console.log(a.author)

Tags: class javascript

Answers

- Konrad
- June 23, 2023 at 7:19 pm
- 0 votes
0
That’s because you can’t have both a property and a getter with the same name

In the first example this.author is a getter and you are trying to overwrite it with this.author = author

In the second example this.author is an unexisting property

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- subdeveloper
- June 23, 2023 at 7:24 pm
- 0 votes
0
Two issues here.

First, in your first example you’re assuming that a getter will implicitly create a field/property. It will not! Thus correct way to use it is:
```
class Book {
  constructor(author) {
    this._author = author;
  }
  // getter
  get author() {
    return this._author;
  }
}
```
Do note that in above code, I have created a property called _author and a getter called author. Thus when you call the getter author it will return the underlying property _author.

Secondly, your second example works, since without you realizing there are actually two properties involved:

this.author and this.writer

Do note that JS is a dynamic language, and it will not complain of non-existent property.

Hope this helps, for more details read about getter and setters in JS here or on other sites!
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