Optional chaining operator (?.) is not supported in IE and other old browsers

[lvxiaodi1234]

In error log monitor，I found some errors like "Uncaught SyntaxError: Unexpected token ." from old browsers（IE and so on）.

Debug file "base.js", the problem is optional chaining operator (?.) can not use directly in old browsers

[sindresorhus]

From the top of the readme:

For browser usage, this package targets the latest version of Chrome, Firefox, and Safari.

[thomasjm]

Using this operator seems to confuse terser for versions < 5.2.0: terser/terser#567

Some parts of the ecosystem still use an older terser, so I think it would be better not to use the optional chaining operator in libraries.