optimize parseLiteral for number-heavy JSON files (ala GeoJSON)

Author: mbullington

src/impl/parser.ts

@@ -482,16 +482,21 @@ export function visit(text: string, visitor: JSONVisitor, options: ParseOptions
 	function parseLiteral(): boolean {
 		switch (_scanner.getToken()) {
 			case SyntaxKind.NumericLiteral:
-				let value = 0;
-				try {
-					value = JSON.parse(_scanner.getTokenValue());
-					if (typeof value !== 'number') {
+				const tokenValue = _scanner.getTokenValue();
+				let value = parseFloat(tokenValue);
+
+				if (isNaN(value)) {
+					try {
+						value = JSON.parse(tokenValue);
+						if (typeof value !== 'number') {
+							handleError(ParseErrorCode.InvalidNumberFormat);
+							value = 0;
+						}
+					} catch (e) {
 						handleError(ParseErrorCode.InvalidNumberFormat);
-						value = 0;
 					}
-				} catch (e) {
-					handleError(ParseErrorCode.InvalidNumberFormat);
 				}
+
 				onLiteralValue(value);
 				break;
 			case SyntaxKind.NullKeyword: