btoa error with special characters

[Tofandel]

• Version: 16.3.0
• Platform: Linux
• Subsystem: Ubuntu

What steps will reproduce the bug?

node -e "console.log(btoa(Buffer.from([0x72, 0xbe, 0x72, 0x91, 0xfb, 0xf6, 0x40, 0x0f, 0x87, 0xc4, 0x45, 0x5e, 0x23, 0xd0, 0x1c, 0xd5])))"

How often does it reproduce? Is there a required condition?

Throws an error

What is the expected behavior?

No error and cr5ykfv2QA+HxEVeI9Ac1Q== logged

What do you see instead?

InvalidCharacterError: Invalid character
      at btoa (node:buffer:1226:7)

The correct implementation of btoa which doesn't throw an error

const btoa = function (str) {
    return Buffer.from(str, 'binary').toString('base64');
};

[targos]

That's because btoa is supposed to be called with a string argument, not a Buffer.
When you pass something that is not a string, it is coerced automatically. With a Buffer, it is done by calling buffer.toString(), which converts the Buffer to a string using UTF-8 encoding. btoa expects Latin-1 encoding.

[Tofandel]

That's a weird spec.. I can see this mentioned in #3462.. I guess custom implementation will still be the preferred way

[kiwavi]

That's because btoa is supposed to be called with a string argument, not a Buffer. When you pass something that is not a string, it is coerced automatically. With a Buffer, it is done by calling buffer.toString(), which converts the Buffer to a string using UTF-8 encoding. btoa expects Latin-1 encoding.

When I pass a string like 𝑯𝒆𝒍𝒍𝒐 I'm getting DOMException [InvalidCharacterError]: Invalid character. Does it only support certain fonts? Thanks