Check type of parsed JSON to determine it's an object and not a number.

lib/util/js.js

@@ -28,9 +28,15 @@ module.exports = {
    * @return {Object|boolean} false if the argument is not a JSON string.
    */
   isValidJSON: function isValidJSON(arg) {
+    var parsed;
     try {
-      return JSON.parse(arg);
+      parsed = JSON.parse(arg);
     } catch (e) {
+      parsed = false;
+    }
+    if (typeof(parsed) === 'object') {
+      return true;
+    } else {
       return false;
     }
   },

test/privatekey.js

@@ -32,7 +32,7 @@ describe('PrivateKey', function() {
     should.exist(b.bn);
   });
 
-  it('should create a privatkey from hexa string', function() {
+  it('should create a privatekey from hexa string', function() {
     var a = new PrivateKey(hex2);
     should.exist(a);
     should.exist(a.bn);

test/util/js.js

@@ -0,0 +1,29 @@
+'use strict';
+/* jshint unused: false */
+
+var should = require('chai').should();
+var expect = require('chai').expect;
+
+var bitcore = require('../..');
+var JSUtil = bitcore.util.js;
+
+describe('js utils', function() {
+
+  describe('isValidJSON', function() {
+    
+    var hexa = '8080808080808080808080808080808080808080808080808080808080808080';
+    var json = '{"key": ["value", "value2"]}';
+
+    it('does not mistake an integer as valid json object', function() {
+      var valid = JSUtil.isValidJSON(hexa);
+      valid.should.equal(false);
+    });
+
+    it('correctly validates a json object', function() {
+      var valid = JSUtil.isValidJSON(json);
+      valid.should.equal(true);
+    });
+
+  });
+
+});