v7.4 for the browser : setup documentation for polyfills

[aavmurphy]

Bug Report

Current Behavior Not sure if this is unclear documentation, or a bug.

• Using Babel (cli) for a website.
• One of the targets is IE11, which does not have (for ... of) and array.prototype.entries
• Used the 'setup' page, 'cli' option (aside: in step 3, the devdependency for cli has the wrong version)

Output is minimised by uglifyjs

The transpiling is all good.

But the js fails in IE11, the array.entries() calls.

Checking the output code, there is no entries() polyfill

Checked the polyfill page. It says the polyfill module is now depreciated.

Either the the setup page / documentation

• doesn't say how to include the polyfills lib, maybe: https://cdnjs.cloudflare.com/ajax/libs/babel-polyfill/7.4.4/polyfill.min.js
• or what config options to inject just the required polyfills into the output-code.

Input Code

for ( let [ i, point ] of points.entries() ) 
{ ... }

Expected behavior/code no js error

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

{
  "presets": [
    ["@babel/preset-env", { "targets":"ie 11" }  ]
    ]
}

Environment

• Babel version(s): 7.4
• Node/npm version: 8.10/3.5.2
• OS: ubuntu
• Monorepo: ?
• How you are using Babel: cli

Possible Solution update documentation

[babel-bot]

Hey @aavmurphy! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack community that typically always has someone willing to help. You can sign-up here for an invite.

[nicolo-ribaudo]

You can use the @babel/preset-env's useBuiltIns option if you are bundling your code; otherwise you'll need to manually import a polyfill (e.g. core-js-bundle or es6-shim + es7-shim)

[pajaydev]

@nicolo-ribaudo can I help in updating the doc ?. If I am not wrong, we need to update it here polyfill.md

[babel-bot]

Hey @aavmurphy! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack community that typically always has someone willing to help. You can sign-up here for an invite.