New option added: stripNull, which removes nulls in serialized output

README.md

@@ -127,6 +127,7 @@ const stringify = fastJson(mySchema, {
 - `rounding`: setup how the `integer` types will be rounded when not integers. [More details](#integer)
 - `largeArrayMechanism`: set the mechanism that should be used to handle large
 (by default `20000` or more items) arrays. [More details](#largearrays)
+- `stripNull`: removes keys with null values from serialised output. If you have lots of null values, using this will result in smallerpayload and improved performance.
 
 
 <a name="api"></a>

index.js

@@ -374,7 +374,7 @@ function buildInnerObject (context, location) {
 
     code += `
       value = obj[${sanitizedKey}]
-      if (value !== undefined) {
+      if ${context.options.stripNull ? '(value != null)' : '(value !== undefined)'} {
         ${addComma}
         json += ${JSON.stringify(sanitizedKey + ':')}
         ${buildValue(context, propertyLocation, 'value')}

test/stripNull.test.js

@@ -0,0 +1,110 @@
+const test = require('tap').test
+const build = require('..')
+
+test('should handle null string values properly', (t) => {
+  t.plan(3)
+
+  const schema = {
+    type: 'object',
+    properties: {
+      firstName: { type: 'string' },
+      lastName: { type: 'string' }
+    },
+    required: ['firstName']
+  }
+  const stringify = build(schema, { stripNull: true })
+
+  const json1 = { firstName: 'Matteo', lastName: 'Collina' }
+  t.equal(stringify(json1), '{"firstName":"Matteo","lastName":"Collina"}')
+
+  const json2 = { firstName: 'Matteo', lastName: null }
+  t.equal(stringify(json2), '{"firstName":"Matteo"}')
+
+  const json3 = { firstName: null, lastName: 'Collina' }
+  t.throws(() => stringify(json3)) // throw error when required property is missing
+})
+
+test('should handle null int values properly', (t) => {
+  t.plan(3)
+
+  const schema = {
+    type: 'object',
+    properties: {
+      name: { type: 'string' },
+      age: { type: 'integer' },
+      experience: { type: 'integer' }
+    }
+  }
+  const stringify = build(schema, { stripNull: true })
+
+  const json1 = { name: 'Matteo', age: 32, experience: 12 }
+  t.equal(stringify(json1), '{"name":"Matteo","age":32,"experience":12}')
+
+  const json2 = { name: 'Matteo', age: null, experience: null }
+  t.equal(stringify(json2), '{"name":"Matteo"}')
+
+  const json3 = { name: 'Matteo', age: 3, experience: null }
+  t.equal(stringify(json3), '{"name":"Matteo","age":3}')
+})
+
+test('should handle arrays properly', (t) => {
+  t.plan(1)
+
+  const schema = {
+    type: 'object',
+    properties: {
+      name: { type: 'string' },
+      experience: {
+        type: 'array',
+        items: {
+          type: 'object',
+          properties: {
+            company: { type: 'string' },
+            years: { type: 'integer' }
+          }
+        }
+      }
+    }
+  }
+  const stringify = build(schema, { stripNull: true })
+
+  const json1 = {
+    name: 'Matteo',
+    experience: [
+      { company: 'C1', years: 12 },
+      { company: 'C2', years: null },
+      { company: null, years: 6 },
+      { company: null, years: null }
+    ]
+  }
+
+  t.equal(
+    stringify(json1),
+    '{"name":"Matteo","experience":[{"company":"C1","years":12},{"company":"C2"},{"years":6},{}]}'
+  )
+})
+
+test('should handle objects and nested objects properly', (t) => {
+  t.plan(2)
+
+  const schema = {
+    type: 'object',
+    properties: {
+      name: { type: 'string' },
+      address: {
+        type: 'object',
+        properties: {
+          city: { type: 'string' },
+          country: { type: 'string' }
+        }
+      }
+    }
+  }
+  const stringify = build(schema, { stripNull: true })
+
+  const json1 = { name: 'Matteo', address: { city: 'Mumbai', country: null } }
+  t.equal(stringify(json1), '{"name":"Matteo","address":{"city":"Mumbai"}}')
+
+  const json2 = { name: null, address: { city: null, country: 'India' } }
+  t.equal(stringify(json2), '{"address":{"country":"India"}}')
+})

types/index.d.ts

@@ -187,6 +187,13 @@ declare namespace build {
      * @default 'default'
      */
     largeArrayMechanism?: 'default' | 'json-stringify'
+
+    /**
+     * Specify if null key-value are removed from serialised JSON output, for a smaller payload
+     *
+     * @default 'false'
+     */
+    stripNull?: boolean
   }
 
   export const validLargeArrayMechanisms: string[]