Enhance validation

Add handling to extreme/sentinel values.

packages/core/src/converter.ts

@@ -75,6 +75,10 @@ export const stringify = <
 		throw new TypeError(`Value must be a string, number, or bigint. Received: ${typeof value}`);
 	}
 
+	if (typeof value === 'number' && Number.isNaN(value)) {
+		return 'NaN';
+	}
+
 	const valueStr = value.toString().replace(/\s/g, '');
 	const { system = enUS.shortCount, stringifyGroupsOptions, mergeTokensOptions } = options;
 
@@ -110,7 +114,16 @@ export interface ParseOptions {
  * @returns AllowedValue The numeric equivalent of the value.
  */
 export const parse = (value: string, options = {} as ParseOptions) => {
-	const { system = enUS.shortCount, type = 'string' } = options;
+	const { system = enUS.shortCount, type: typeRaw = 'string' } = options;
+	const type = typeRaw.trim().toLowerCase() as ParseResult;
+
+	if (!((ALLOWED_PARSE_RESULT_TYPES as unknown as string[]).includes(type))) {
+		throw new TypeError(`Return type must be a string, number, or bigint. Received: ${type}`);
+	}
+
+	if (value.trim().toLowerCase() === 'nan') {
+		return type === 'number' ? NaN : 'NaN';
+	}
 
 	const tokens = system.tokenize(value);
 	const { groups, negative } = system.parseGroups(tokens);
@@ -124,6 +137,7 @@ export const parse = (value: string, options = {} as ParseOptions) => {
 			const exponentValue = Number(exponent);
 			const integerValue = Number(integer);
 
+			// max safe integer: 9.007199254740991e+15
 			const [maxSafeIntegerSignificand, maxSafeIntegerExponent] = Number.MAX_SAFE_INTEGER.toExponential().split('e');
 			if (
 				exponentValue >= Number(maxSafeIntegerExponent)
@@ -136,6 +150,7 @@ export const parse = (value: string, options = {} as ParseOptions) => {
 				return stringValue;
 			}
 
+			// epsilon: 2.220446049250313e-16
 			const [epsilonSignificand, epsilonExponent] = Number.EPSILON.toExponential().split('e');
 			if (
 				exponentValue <= Number(epsilonExponent)