call toJSON method on object types

index.js

@@ -554,9 +554,17 @@ function addIfThenElse (schema, name, externalSchema, fullSchema) {
   return { code: code, laterCode: laterCode }
 }
 
+function toJSON (variableName) {
+  return `typeof ${variableName}.toJSON === 'function' 
+    ? ${variableName}.toJSON() 
+    : ${variableName}
+  `
+}
+
 function buildObject (schema, code, name, externalSchema, fullSchema) {
   code += `
-    function ${name} (obj) {
+    function ${name} (input) {
+      var obj = ${toJSON('input')}
       var json = '{'
       var addComma = false
   `

test/toJSON.test.js

@@ -0,0 +1,83 @@
+'use strict'
+
+const test = require('tap').test
+const build = require('..')
+
+test('use toJSON method on object types', (t) => {
+  t.plan(1)
+
+  const stringify = build({
+    title: 'simple object',
+    type: 'object',
+    properties: {
+      productName: {
+        type: 'string'
+      }
+    }
+  })
+  const object = {
+    product: { name: 'cola' },
+    toJSON: function () {
+      return { productName: this.product.name }
+    }
+  }
+
+  t.equal('{"productName":"cola"}', stringify(object))
+})
+
+test('use toJSON method on nested object types', (t) => {
+  t.plan(1)
+
+  const stringify = build({
+    title: 'simple array',
+    type: 'array',
+    items: {
+      type: 'object',
+      properties: {
+        productName: {
+          type: 'string'
+        }
+      }
+    }
+  })
+  const array = [
+    {
+      product: { name: 'cola' },
+      toJSON: function () {
+        return { productName: this.product.name }
+      }
+    },
+    {
+      product: { name: 'sprite' },
+      toJSON: function () {
+        return { productName: this.product.name }
+      }
+    }
+  ]
+
+  t.equal('[{"productName":"cola"},{"productName":"sprite"}]', stringify(array))
+})
+
+test('not use toJSON if does not exist', (t) => {
+  t.plan(1)
+
+  const stringify = build({
+    title: 'simple object',
+    type: 'object',
+    properties: {
+      product: {
+        type: 'object',
+        properties: {
+          name: {
+            type: 'string'
+          }
+        }
+      }
+    }
+  })
+  const object = {
+    product: { name: 'cola' }
+  }
+
+  t.equal('{"product":{"name":"cola"}}', stringify(object))
+})