Added BigInt support (#197)

* Added BigInt support

* Updated test

* Updated README

Author: delvedor

README.md

@@ -106,6 +106,7 @@ And nested ones, too.
 | -----------|------------------------------|
 | `Date`     | `string` via `toISOString()` |
 | `RegExp`   | `string`                     |
+| `BigInt`   | `integer` via `toString`     |
 
 <a name="required"></a>
 #### Required
@@ -439,9 +440,28 @@ const stringify = fastJson(schema, { schema: externalSchema })
 
 <a name="long"></a>
 #### Long integers
-Long integers (64-bit) are supported using the [long](https://github.com/dcodeIO/long.js) module.
+By default the library will handle automatically [BigInt](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt) from Node.js v10.3 and above.  
+If you can't use BigInts in your environment, long integers (64-bit) are also supported using the [long](https://github.com/dcodeIO/long.js) module.
 Example:
 ```javascript
+// => using native BigInt
+const stringify = fastJson({
+  title: 'Example Schema',
+  type: 'object',
+  properties: {
+    id: {
+      type: 'integer'
+    }
+  }
+})
+
+const obj = {
+  id: 18446744073709551615n
+}
+
+console.log(stringify(obj)) // '{"id":18446744073709551615}'
+
+// => using the long library
 const Long = require('long')
 
 const stringify = fastJson({

index.js

@@ -214,6 +214,8 @@ function $asNull () {
 function $asInteger (i) {
   if (isLong && isLong(i)) {
     return i.toString()
+  } else if (typeof i === 'bigint') {
+    return i.toString()
   } else {
     return $asNumber(i)
   }

package.json

@@ -39,6 +39,7 @@
     "long": "^4.0.0",
     "pre-commit": "^1.2.2",
     "proxyquire": "^2.1.3",
+    "semver": "^6.3.0",
     "standard": "^14.0.0",
     "tap": "^12.6.5",
     "tap-mocha-reporter": "^3.0.9",

test/bigint.js

@@ -0,0 +1,74 @@
+'use strict'
+
+module.exports = function (test, build) {
+  test('render a bigint as JSON', (t) => {
+    t.plan(1)
+
+    const schema = {
+      title: 'bigint',
+      type: 'integer'
+    }
+
+    const stringify = build(schema)
+    const output = stringify(1615n)
+
+    t.equal(output, '1615')
+  })
+
+  test('render an object with a bigint as JSON', (t) => {
+    t.plan(1)
+
+    const schema = {
+      title: 'object with bigint',
+      type: 'object',
+      properties: {
+        id: {
+          type: 'integer'
+        }
+      }
+    }
+
+    const stringify = build(schema)
+    const output = stringify({
+      id: 1615n
+    })
+
+    t.equal(output, '{"id":1615}')
+  })
+
+  test('render an array with a bigint as JSON', (t) => {
+    t.plan(1)
+
+    const schema = {
+      title: 'array with bigint',
+      type: 'array',
+      items: {
+        type: 'integer'
+      }
+    }
+
+    const stringify = build(schema)
+    const output = stringify([1615n])
+
+    t.equal(output, '[1615]')
+  })
+
+  test('render an object with an additionalProperty of type bigint as JSON', (t) => {
+    t.plan(1)
+
+    const schema = {
+      title: 'object with bigint',
+      type: 'object',
+      additionalProperties: {
+        type: 'integer'
+      }
+    }
+
+    const stringify = build(schema)
+    const output = stringify({
+      num: 1615n
+    })
+
+    t.equal(output, '{"num":1615}')
+  })
+}

test/integer.test.js

@@ -1,6 +1,8 @@
 'use strict'
 
-const test = require('tap').test
+const t = require('tap')
+const test = t.test
+const semver = require('semver')
 const validator = require('is-my-json-valid')
 const proxyquire = require('proxyquire')
 const build = proxyquire('..', { long: null })
@@ -83,3 +85,10 @@ test('render an object with an additionalProperty of type integer as JSON', (t)
   t.equal(output, '{"num":1615}')
   t.ok(validate(JSON.parse(output)), 'valid schema')
 })
+
+if (semver.gt(process.versions.node, '10.3.0')) {
+  require('./bigint')(t.test, build)
+} else {
+  t.pass('Skip because Node version < 10.4')
+  t.end()
+}