Adds BigInt support to stringify util function (#4112)

Author: jjsfernandez

lib/utils.js

@@ -298,6 +298,9 @@ function jsonStringify(object, spaces, depth) {
             ? '-0'
             : val.toString();
         break;
+      case 'bigint':
+        val = val.toString() + 'n';
+        break;
       case 'date':
         var sDate = isNaN(val.getTime()) ? val.toString() : val.toISOString();
         val = '[Date: ' + sDate + ']';

test/unit/utils.spec.js

@@ -1,3 +1,4 @@
+/* global BigInt */
 'use strict';
 
 var utils = require('../../lib/utils');
@@ -204,6 +205,13 @@ describe('lib/utils', function() {
         expect(stringify(1.2), 'to be', '1.2');
         expect(stringify(1e9), 'to be', '1000000000');
       });
+
+      if (typeof BigInt === 'function') {
+        it('should work with bigints when possible', function() {
+          expect(stringify(BigInt(1)), 'to be', '1n');
+          expect(stringify(BigInt(2)), 'to be', '2n');
+        });
+      }
     });
 
     describe('canonicalize example', function() {