Bug Report

Current Behavior

The output is undefined in IE10.

Input Code

function A() {}
A.prototype.a = 'aaa';

class B extends A {}
console.log(B.prototype.a);

Expected behavior/code

Expect output aaa, but got undefined in IE10. I also tested this in @vue/cli@3.0.0-beta.9, it have the same problem.

Babel Configuration (.babelrc, package.json, cli command)

Environment

• Babel version(s): v7.0.0-beta.36
• Node/npm version: Node 8/npm 5
• OS: OSX 10.13.4
• Monorepo [e.g. yes/no/Lerna]
• How you are using Babel: [e.g. cli, register, loader]

Possible Solution

Additional context/Screenshots