Error in IE11 caused by babel polyfill - delegate.iterator.return


Hope to get some help with following:

<h2><strong>The problem</strong></h2>

@babel/polyfill causes error in IE11:

SCRIPT1010: Expected identifier

Debugger point on the line:

if (delegate.iterator.return) {

in the function maybeInvokeDelegate() in regenerator-runtime plugin.


Problem occures <strong>only in test environment</strong>. When I run my aplication locally, with exactly same build, same browser it works just fine. It contains same code, but it doesn't break anything.

<h2><strong>What I've already tried:</strong></h2> <ol><li>

<a href="https://babeljs.io/docs/en/next/babel-plugin-transform-member-expression-literals.html" rel="nofollow">babel-plugin-transform-member-expression-literals</a> doesn't seem to help.

</li> <li>

I tried to replace @babel/polyfill with only necessary polyfills but I failed. To much errors breaking application which are hard to catch/debug/understand.

</li> <li>

Set useBuiltIns: "usage" in .babelrc but faced a problem with way it imports necessary modules. I'm going to give this one more try.

</li> <li>

I looked through all same issues with regeerator-runtime and babel-polyfill on github, but haven't found working solution.

</li> </ol><h2><strong>Config</strong></h2>

At the moment I'm requiring @babel/polyfill in webpack config and use it as an entry point. I believe I don't even need regenerator-runtime, because as far as I understand it used for async function (maybe I'm mistaken) and we don't use them.

I'm not using babel loader for webpack but run babel for /dist directory after webpack.

<strong>My babelrc:</strong>

{ plugins: ["transform-member-expression-literals"], presets: [ [ "@babel/preset-env", { useBuiltIns: "entry", modules: "false", targets: { ie: 11 } }] ] }


require("@babel/polyfill") const getDefaultConfig = env => ({ mode: "development", entry: ["whatwg-fetch", "@babel/polyfill", "./src/index.js"], ... })

I have updated all babel packages to latest versions.

Appreciate any help or ideas.


Take a look at the link below

<a href="http://github.com/facebook/create-react-app/issues/4255" rel="nofollow">github.com/facebook/create-react-app/issues/4255</a>


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