Syntax Regular Expression Error in IE

[babel-bot]

Original issue submitted by @Chun-MingChen in babel/babel#9380

Bug Report

Current Behavior

core-js@2.6.x start support sticky flag y in modules/es6.regexp.split.js
Unfortunately, this feature IE didn't support (see http://kangax.github.io/compat-table/es6/#test-RegExp_y_and_u_flags).

SCRIPT5017: Syntax error in regular expression

ref: https://github.com/getify/You-Dont-Know-JS/blob/master/es6%20&%20beyond/ch2.md#sticky-flag

Possible Solution
Remove ^ in package.json.

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

{
  "name": "@babel/polyfill",
  "dependencies": {
-   "core-js": "^2.5.7",
+   "core-js": "2.5.7",
    "regenerator-runtime": "^0.12.0"
  }
}

Environment

• Babel version(s): 6.5.2
• Node/npm version: 8.14.0

[zloirock]

@Chun-MingChen @waynelai614 could you add a code which causes a problem?

[waynelai614]

@zloirock
This line

var SUPPORTS_Y = !!(function () { try { return new RegExp('x', 'y'); } catch (e) {} })();

https://github.com/zloirock/core-js/blob/v2/modules/es6.regexp.split.js#L17

IE didn't support both new RegExp('x', 'y') and /x/y

I'll cause error start from core-js@2.6.0 (#411)

same issue from #372

[zloirock]

It's calling of RegExp constructor, not syntax construction, and try / catch block catch this error. core-js tested and works in IE. So, please, add a reproducible example.

[zloirock]

Maybe the problem in minified code and your minifier transpile new RegExp('x', 'y') -> /x/y?

[waynelai614]

@zloirock
yes, you're right.
The problem is our minified code compress it to /x/y 😢

REPL link

[zloirock]

Ok, I'll try to add a workaround for that.

[zloirock]

Also, it should be fixed on babel side because core-js is not the only place where used this feature detection.

[zloirock]

It's already filed babel/minify#928

[waynelai614]

@zloirock
Thanks for the quick fix, hope you find a good job soon 😃

[chunming-c]

It's already filed babel/minify#928

Nice work and great speed 🎉