Enable loose mode for class-properties (facebook#4248)

* Enable loose mode for `class-properties` * Update comment to point to discussion Resolves facebook#4263

Author: rgrochowicz

packages/babel-preset-react-app/index.js

@@ -92,7 +92,14 @@ module.exports = function(api, opts) {
  // don't work without it: https://github.com/babel/babel/issues/7215
  require('@babel/plugin-transform-destructuring').default,
  // class { handleClick = () => { } }
- require('@babel/plugin-proposal-class-properties').default,
+ // Enable loose mode to use assignment instead of defineProperty
+ // See discussion in https://github.com/facebook/create-react-app/issues/4263
+ [
+ require('@babel/plugin-proposal-class-properties').default,
+ {
+ loose: true,
+ },
+ ],
  // The following two plugins use Object.assign directly, instead of Babel's
  // extends helper. Note that this assumes `Object.assign` is available.
  // { ...todo, completed: true }