Sometimes we can’t implement a solution that’s fully spec-compliant, and in those cases using a polyfill might be the wrong answer. A polyfill would translate into telling the rest of the codebase that it’s okay to use the feature, that it’ll work just like in modern browsers, but it might not in edge cases.

IDEs and standard *nix tools like sed can help, but you typically have to make a trade-off between introducing errors and introducing tedium.

You can but it's difficult. I recommend switching to a different tool.