OptionalallowOptionalbigGenerates a bigint value if the string represents
a valid integer too large for the number type.
OptionaldecimalSpecifies which character ("." or ",") to treat as the decimal separator.
OptionalromanAttempt to parse Roman numerals if Arabic numeral parsing fails.
OptionalroundRound the result to this many decimal places. Defaults to 3; must be greater than or equal to zero.
Allow and ignore trailing invalid characters à la
parseFloat.