ES6 getter/setter with arrow function

ecmascript-6 babeljs
Gabor Dolla picture Gabor Dolla · Nov 20, 2015 · Viewed 26.7k times · Source

I'm using babel6 and for my pet project I'm creating a wrapper for XMLHttpRequest, for the methods I can use:

open = (method, url, something) => {
  return this.xhr.open(method, url, something);
}

but for the properties arrow function doesn't work

this works:

get status() { return this.xhr.status; }

but I can not use

get status = () => this.xhr.status;

Is this intentional?

Answer

apsillers picture apsillers · Nov 20, 2015

According to the ES2015 grammar, a property on an object literal can only be one of four things:

PropertyDefinition:

  • IdentifierReference
  • PropertyName : AssignmentExpression
  • MethodDefinition

The only one of these type that allows a leading get is MethodDefinition:

MethodDefinition :

  • PropertyName ( StrictFormalParameters ) { FunctionBody }
  • GeneratorMethod
  • get PropertyName ( ) { FunctionBody }
  • set PropertyName ( PropertySetParameterList ) { FunctionBody }

As you can see, the get form follows a very limited grammar that must be of the form

get NAME () { BODY }

The grammar does not allow functions of the form get NAME = ....

Related questions

Using Node.js require vs. ES6 import/export

In a project I'm collaborating on, we have two choices on which module system we can use: Importing modules using require, and exporting using module.exports and exports.foo. Importing modules using ES6 import, and exporting using ES6 export Are …

Read More
Getting Unexpected Token Export

I am trying to run some ES6 code in my project but I am getting an unexpected token export error. export class MyClass { constructor() { console.log("es6"); } }

Read More
"unexpected token import" in Nodejs5 and babel?

In js file, i used import to instead of require import co from 'co'; And tried to run it directly by nodejs since it said import is 'shipping features' and support without any runtime flag (https://nodejs.org/en/docs/…

Read More