Resolves #7

Author: Faleij

.vscode/launch.json

@@ -0,0 +1,18 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "type": "node",
+            "request": "launch",
+            "name": "Debug Mocha",
+            "program": "${workspaceFolder}\\node_modules\\mocha\\bin\\_mocha",
+            "stopOnEntry": false,
+            "args": ["-R", "spec", "-b"],
+            "cwd": "${workspaceFolder}",
+            "runtimeExecutable": null
+        }
+    ]
+}

package.json

@@ -1,7 +1,7 @@
 {
   "name": "json-stream-stringify",
   "description": "JSON.Stringify as a readable stream",
-  "version": "2.0.0",
+  "version": "2.0.1",
   "license": "MIT",
   "author": "Faleij <faleij@gmail.com> (https://github.com/faleij)",
   "repository": {

src/JsonStreamStringify.js

@@ -120,7 +120,7 @@ class JsonStreamStringify extends Readable {
     return value;
   }
 
-  addToStack(value, key, index) {
+  addToStack(value, key, index, parent) {
     let realValue = value;
     if (this.replacerFunction) {
       realValue = this.replacerFunction(key || index, realValue, this);
@@ -138,6 +138,13 @@ class JsonStreamStringify extends Readable {
       }
     }
     let type = getType(realValue);
+    if (((parent && parent.type === 'Array') ? true : realValue !== undefined) && type !== 'Promise') {
+      if (parent && !parent.first) {
+        this._push(',');
+      }
+      /* eslint-disable-next-line no-param-reassign */
+      if (parent) parent.first = false;
+    }
     if (realValue !== undefined && type !== 'Promise' && key) {
       if (this.gap) {
         this._push(`\n${this.gap.repeat(this.depth)}"${escapeString(key)}": `);
@@ -172,6 +179,8 @@ class JsonStreamStringify extends Readable {
       index,
       type,
       value: realValue,
+      parent,
+      first: true,
     };
 
     if (type === 'Object') {
@@ -199,7 +208,6 @@ class JsonStreamStringify extends Readable {
         this.error = true;
         this.emit('error', err);
       });
-      obj.first = true;
     }
     this.stack.unshift(obj);
     return obj;
@@ -222,10 +230,8 @@ class JsonStreamStringify extends Readable {
     const end = stackItemEnd[type];
     if (isObject && !item.isEmpty && this.gap) this._push(`\n${this.gap.repeat(this.depth)}`);
     if (end) this._push(end);
-    if (item.addSeparatorAfterEnd) {
-      this._push(',');
-    }
-    this.stack.splice(this.stack.indexOf(item), 1);
+    const stackIndex = this.stack.indexOf(item);
+    this.stack.splice(stackIndex, 1);
   }
 
   _push(data) {
@@ -254,14 +260,15 @@ class JsonStreamStringify extends Readable {
   }
 
   processObject(current) {
+    // when no keys left, remove obj from stack
     if (!current.unread.length) {
       this.removeFromStack(current);
       return;
     }
     const key = current.unread.shift();
     const value = current.value[key];
 
-    this.addToStack(value, current.type === 'Object' && key, current.type === 'Array' && key).addSeparatorAfterEnd = !!current.unread.length;
+    this.addToStack(value, current.type === 'Object' && key, current.type === 'Array' && key, current);
   }
 
   processArray(current) {
@@ -319,14 +326,8 @@ class JsonStreamStringify extends Readable {
 
   processPromise(current) {
     return recursiveResolve(current.value).then((value) => {
-      const {
-        addSeparatorAfterEnd,
-      } = current;
-      /* eslint-disable-next-line no-param-reassign */
-      current.addSeparatorAfterEnd = false;
       this.removeFromStack(current);
-      this.addToStack(value, current.key, current.index)
-        .addSeparatorAfterEnd = addSeparatorAfterEnd;
+      this.addToStack(value, current.key, current.index, current.parent);
     });
   }
 

test-src/JsonStreamStringify.spec.js

@@ -84,6 +84,23 @@ describe('JsonStreamStringify', () => {
     return v;
   }));
 
+  it('{a:1, b:2} should be {"a":1}', createTest({
+    a: 1,
+    b: 2,
+  }, '{"a":1}', (k, v) => {
+    if (k === 'a') {
+      expect(v).to.be(1);
+      return v;
+    }
+    if (k === 'b') {
+      expect(v).to.be(2);
+      return undefined;
+    }
+    if (k === undefined) return v;
+    expect(['a', 'b', undefined]).to.contain(k);
+    return v;
+  }));
+
   it('{a:1,b:2} should be {"b":2}', createTest({
     a: 1,
     b: 2,
@@ -93,11 +110,24 @@ describe('JsonStreamStringify', () => {
     a: 1,
   }, '{"a":1}'));
 
-  it('{a:function(){}} should be {}', createTest({
+  it('{a:1,b:undefined} should be {"a":1}', createTest({
+    a: 1,
+    b: undefined,
+  }, '{"a":1}'));
+
+  it('{a:1,b:Promise(undefined)} should be {"a":1}', createTest({
+    a: 1,
+    b: Promise.resolve(undefined),
+  }, '{"a":1}'));
+
+  it('{a:function(){}, b: "b"} should be {"b": "b"}', createTest({
     a() {},
-  }, '{}'));
+    b: 'b',
+  }, '{"b":"b"}'));
 
   it('[function(){}] should be [null]', createTest([function a() {}], '[null]'));
+  
+  it('[function(){}, undefined] should be [null,null]', createTest([function a() {}, undefined], '[null,null]'));
 
   it('{a:date} should be {"a":date.toJSON()}', createTest({
     a: date,