Cannot use defined Unit using ° (U+00B0)

[modellking]

Documentation states that the only barrier to adding extended character support is overwriting the Unit.isValidAlpha method (https://mathjs.org/docs/datatypes/units.html#support-of-custom-characters-in-unit-names)

The following code produces an Error

const isAlphaOriginal = math.Unit.isValidAlpha
const isDegOrPercent = function (c) {
    return c === "°" || c === "%"
}
math.Unit.isValidAlpha = function (c) {
    return isAlphaOriginal(c) || isDegOrPercent(c)
}
math.createUnit('°', '1 deg')
math.createUnit('%', '0.01')

math.evaluate('12.7 ° to deg')

Error:
SyntaxError: Syntax error in part "° to deg"

This is reproducible in the demo JSBin (2021-11-15) and Version 9.4.1

Thank you for your library.

[josdejong]

You'll also have to override the isAlpha of the expression parser, math.expression.parse.isAlpha.

See #1268