The JavaScript exception "form must be one of 'NFC', 'NFD', 'NFKC', or 'NFKD'" occurs when an unrecognized string is passed to theString.prototype.normalize() method.

Message

RangeError: The normalization form should be one of NFC, NFD, NFKC, NFKD. (V8-based)RangeError: form must be one of 'NFC', 'NFD', 'NFKC', or 'NFKD' (Firefox)RangeError: argument does not match any normalization form (Safari)

Error type

What went wrong?

TheString.prototype.normalize() method only accepts the following four values as itsform argument:"NFC","NFD","NFKC", or"NFKD". If you pass any other value, an error will be thrown. Read the reference ofnormalize() to learn about different normalization forms.

Examples

Invalid cases

"foo".normalize("nfc"); // RangeError"foo".normalize(" NFC "); // RangeError

Valid cases

"foo".normalize("NFC"); // 'foo'

See also

• String.prototype.normalize()