From 57c489591cf1e5b8ef4f2591848b54448ff19b46 Mon Sep 17 00:00:00 2001
From: Ferit <frtcm11@gmail.com>
Date: Sun, 11 Oct 2026 18:05:36 +0300
Subject: [PATCH] fix: delete properties when reviver returns undefined

---
 cjs/index.js  | 14 +++++++++++---
 es.js         |  2 +-
 esm.js        |  2 +-
 esm/index.js  | 14 +++++++++++---
 index.js      | 10 +++++++---
 min.js        |  2 +-
 test/index.js | 21 +++++++++++++++++++++
 7 files changed, 53 insertions(+), 12 deletions(-)

diff --git a/cjs/index.js b/cjs/index.js
index a4833a5..74aafd2 100644
--- a/cjs/index.js
+++ b/cjs/index.js
@@ -22,6 +22,14 @@ const Primitives = (_, value) => (
   typeof value === primitive ? new Primitive(value) : value
 );
 
+const reviveProperty = (output, key, value, reviver) => {
+  const revived = reviver.call(output, key, value);
+  if (revived === void 0)
+    delete output[key];
+  else
+    output[key] = revived;
+};
+
 const resolver = (input, lazy, parsed, $) => output => {
   for (let ke = keys(output), {length} = ke, y = 0; y < length; y++) {
     const k = ke[y];
@@ -34,10 +42,10 @@ const resolver = (input, lazy, parsed, $) => output => {
         lazy.push({ o: output, k, r: tmp });
       }
       else
-        output[k] = $.call(output, k, tmp);
+        reviveProperty(output, k, tmp, $);
     }
     else if (output[k] !== ignore)
-      output[k] = $.call(output, k, value);
+      reviveProperty(output, k, value, $);
   }
   return output;
 };
@@ -69,7 +77,7 @@ const parse = (text, reviver) => {
     while (i < lazy.length) {
       // it could be a lazy.shift() but that's costly
       const {o, k, r} = lazy[i++];
-      o[k] = $.call(o, k, revive(r));
+      reviveProperty(o, k, revive(r), $);
     }
   }
 
diff --git a/es.js b/es.js
index 3e4d187..17689a9 100644
--- a/es.js
+++ b/es.js
@@ -1 +1 @@
-self.Flatted=function(t){"use strict";const{parse:e,stringify:n}=JSON,{keys:r}=Object,o=String,s="string",c={},l="object",f=(t,e)=>e,i=t=>t instanceof o?o(t):t,a=(t,e)=>typeof e===s?new o(e):e,u=(t,e,n)=>{const r=o(e.push(n)-1);return t.set(n,r),r},p=(t,n)=>{const s=e(t,a).map(i),u=n||f;let p=s[0];if(typeof p===l&&p){const t=[],e=((t,e,n,s)=>f=>{for(let i=r(f),{length:a}=i,u=0;u<a;u++){const r=i[u],a=f[r];if(a instanceof o){const o=t[+a];typeof o!==l||n.has(o)?f[r]=s.call(f,r,o):(n.add(o),f[r]=c,e.push({o:f,k:r,r:o}))}else f[r]!==c&&(f[r]=s.call(f,r,a))}return f})(s,t,new Set,u);p=e(p);let n=0;for(;n<t.length;){const{o:r,k:o,r:s}=t[n++];r[o]=u.call(r,o,e(s))}}return u.call({"":p},"",p)},g=(t,e,r)=>{const o=e&&typeof e===l?(t,n)=>""===t||-1<e.indexOf(t)?n:void 0:e||f,c=new Map,i=[],a=[];let p=+u(c,i,o.call({"":t},"",t)),g=!p;for(;p<i.length;)g=!0,a[p]=n(i[p++],h,r);return"["+a.join(",")+"]";function h(t,e){if(g)return g=!g,e;const n=o.call(this,t,e);switch(typeof n){case l:if(null===n)return n;case s:return c.get(n)||u(c,i,n)}return n}};return t.fromJSON=t=>p(n(t)),t.parse=p,t.stringify=g,t.toJSON=t=>e(g(t)),t}({});
+self.Flatted=function(t){"use strict";const{parse:e,stringify:n}=JSON,{keys:r}=Object,o=String,s="string",c={},i="object",f=(t,e)=>e,l=t=>t instanceof o?o(t):t,a=(t,e)=>typeof e===s?new o(e):e,u=(t,e,n,r)=>{const o=r.call(t,e,n);void 0===o?delete t[e]:t[e]=o},p=(t,e,n)=>{const r=o(e.push(n)-1);return t.set(n,r),r},g=(t,n)=>{const s=e(t,a).map(l),p=n||f;let g=s[0];if(typeof g===i&&g){const t=[],e=((t,e,n,s)=>f=>{for(let l=r(f),{length:a}=l,p=0;p<a;p++){const r=l[p],a=f[r];if(a instanceof o){const o=t[+a];typeof o!==i||n.has(o)?u(f,r,o,s):(n.add(o),f[r]=c,e.push({o:f,k:r,r:o}))}else f[r]!==c&&u(f,r,a,s)}return f})(s,t,new Set,p);g=e(g);let n=0;for(;n<t.length;){const{o:r,k:o,r:s}=t[n++];u(r,o,e(s),p)}}return p.call({"":g},"",g)},h=(t,e,r)=>{const o=e&&typeof e===i?(t,n)=>""===t||-1<e.indexOf(t)?n:void 0:e||f,c=new Map,l=[],a=[];let u=+p(c,l,o.call({"":t},"",t)),g=!u;for(;u<l.length;)g=!0,a[u]=n(l[u++],h,r);return"["+a.join(",")+"]";function h(t,e){if(g)return g=!g,e;const n=o.call(this,t,e);switch(typeof n){case i:if(null===n)return n;case s:return c.get(n)||p(c,l,n)}return n}};return t.fromJSON=t=>g(n(t)),t.parse=g,t.stringify=h,t.toJSON=t=>e(h(t)),t}({});
diff --git a/esm.js b/esm.js
index 2563a41..b6a65e8 100644
--- a/esm.js
+++ b/esm.js
@@ -1 +1 @@
-const{parse:t,stringify:e}=JSON,{keys:n}=Object,o=String,r="string",s={},c="object",l=(t,e)=>e,f=t=>t instanceof o?o(t):t,i=(t,e)=>typeof e===r?new o(e):e,a=(t,e,n)=>{const r=o(e.push(n)-1);return t.set(n,r),r},u=(e,r)=>{const a=t(e,i).map(f),u=r||l;let p=a[0];if(typeof p===c&&p){const t=[],e=((t,e,r,l)=>f=>{for(let i=n(f),{length:a}=i,u=0;u<a;u++){const n=i[u],a=f[n];if(a instanceof o){const o=t[+a];typeof o!==c||r.has(o)?f[n]=l.call(f,n,o):(r.add(o),f[n]=s,e.push({o:f,k:n,r:o}))}else f[n]!==s&&(f[n]=l.call(f,n,a))}return f})(a,t,new Set,u);p=e(p);let r=0;for(;r<t.length;){const{o:n,k:o,r:s}=t[r++];n[o]=u.call(n,o,e(s))}}return u.call({"":p},"",p)},p=(t,n,o)=>{const s=n&&typeof n===c?(t,e)=>""===t||-1<n.indexOf(t)?e:void 0:n||l,f=new Map,i=[],u=[];let p=+a(f,i,s.call({"":t},"",t)),h=!p;for(;p<i.length;)h=!0,u[p]=e(i[p++],g,o);return"["+u.join(",")+"]";function g(t,e){if(h)return h=!h,e;const n=s.call(this,t,e);switch(typeof n){case c:if(null===n)return n;case r:return f.get(n)||a(f,i,n)}return n}},h=e=>t(p(e)),g=t=>u(e(t));export{g as fromJSON,u as parse,p as stringify,h as toJSON};
+const{parse:t,stringify:e}=JSON,{keys:n}=Object,o=String,r="string",s={},c="object",l=(t,e)=>e,f=t=>t instanceof o?o(t):t,i=(t,e)=>typeof e===r?new o(e):e,a=(t,e,n,o)=>{const r=o.call(t,e,n);void 0===r?delete t[e]:t[e]=r},u=(t,e,n)=>{const r=o(e.push(n)-1);return t.set(n,r),r},p=(e,r)=>{const u=t(e,i).map(f),p=r||l;let h=u[0];if(typeof h===c&&h){const t=[],e=((t,e,r,l)=>f=>{for(let i=n(f),{length:u}=i,p=0;p<u;p++){const n=i[p],u=f[n];if(u instanceof o){const o=t[+u];typeof o!==c||r.has(o)?a(f,n,o,l):(r.add(o),f[n]=s,e.push({o:f,k:n,r:o}))}else f[n]!==s&&a(f,n,u,l)}return f})(u,t,new Set,p);h=e(h);let r=0;for(;r<t.length;){const{o:n,k:o,r:s}=t[r++];a(n,o,e(s),p)}}return p.call({"":h},"",h)},h=(t,n,o)=>{const s=n&&typeof n===c?(t,e)=>""===t||-1<n.indexOf(t)?e:void 0:n||l,f=new Map,i=[],a=[];let p=+u(f,i,s.call({"":t},"",t)),h=!p;for(;p<i.length;)h=!0,a[p]=e(i[p++],g,o);return"["+a.join(",")+"]";function g(t,e){if(h)return h=!h,e;const n=s.call(this,t,e);switch(typeof n){case c:if(null===n)return n;case r:return f.get(n)||u(f,i,n)}return n}},g=e=>t(h(e)),y=t=>p(e(t));export{y as fromJSON,p as parse,h as stringify,g as toJSON};
diff --git a/esm/index.js b/esm/index.js
index eb2da2d..073b5f5 100644
--- a/esm/index.js
+++ b/esm/index.js
@@ -21,6 +21,14 @@ const Primitives = (_, value) => (
   typeof value === primitive ? new Primitive(value) : value
 );
 
+const reviveProperty = (output, key, value, reviver) => {
+  const revived = reviver.call(output, key, value);
+  if (revived === void 0)
+    delete output[key];
+  else
+    output[key] = revived;
+};
+
 const resolver = (input, lazy, parsed, $) => output => {
   for (let ke = keys(output), {length} = ke, y = 0; y < length; y++) {
     const k = ke[y];
@@ -33,10 +41,10 @@ const resolver = (input, lazy, parsed, $) => output => {
         lazy.push({ o: output, k, r: tmp });
       }
       else
-        output[k] = $.call(output, k, tmp);
+        reviveProperty(output, k, tmp, $);
     }
     else if (output[k] !== ignore)
-      output[k] = $.call(output, k, value);
+      reviveProperty(output, k, value, $);
   }
   return output;
 };
@@ -68,7 +76,7 @@ export const parse = (text, reviver) => {
     while (i < lazy.length) {
       // it could be a lazy.shift() but that's costly
       const {o, k, r} = lazy[i++];
-      o[k] = $.call(o, k, revive(r));
+      reviveProperty(o, k, revive(r), $);
     }
   }
 
diff --git a/index.js b/index.js
index 9386548..69064b6 100644
--- a/index.js
+++ b/index.js
@@ -32,6 +32,10 @@ self.Flatted = (function (exports) {
   var Primitives = function Primitives(_, value) {
     return _typeof(value) === primitive ? new Primitive(value) : value;
   };
+  var reviveProperty = function reviveProperty(output, key, value, reviver) {
+    var revived = reviver.call(output, key, value);
+    if (revived === void 0) delete output[key];else output[key] = revived;
+  };
   var resolver = function resolver(input, lazy, parsed, $) {
     return function (output) {
       for (var ke = keys(output), length = ke.length, y = 0; y < length; y++) {
@@ -47,8 +51,8 @@ self.Flatted = (function (exports) {
               k: k,
               r: tmp
             });
-          } else output[k] = $.call(output, k, tmp);
-        } else if (output[k] !== ignore) output[k] = $.call(output, k, value);
+          } else reviveProperty(output, k, tmp, $);
+        } else if (output[k] !== ignore) reviveProperty(output, k, value, $);
       }
       return output;
     };
@@ -80,7 +84,7 @@ self.Flatted = (function (exports) {
           o = _lazy$i.o,
           k = _lazy$i.k,
           r = _lazy$i.r;
-        o[k] = $.call(o, k, revive(r));
+        reviveProperty(o, k, revive(r), $);
       }
     }
     return $.call({
diff --git a/min.js b/min.js
index d3a97cb..d0d3ff1 100644
--- a/min.js
+++ b/min.js
@@ -1 +1 @@
-self.Flatted=function(n){"use strict";function t(n){return t="function"==typeof Symbol&&"symbol"==typeof Symbol.iterator?function(n){return typeof n}:function(n){return n&&"function"==typeof Symbol&&n.constructor===Symbol&&n!==Symbol.prototype?"symbol":typeof n},t(n)}var r=JSON.parse,e=JSON.stringify,o=Object.keys,u=String,f="string",i={},c="object",a=function(n,t){return t},l=function(n){return n instanceof u?u(n):n},s=function(n,r){return t(r)===f?new u(r):r},y=function(n,t,r){var e=u(t.push(r)-1);return n.set(r,e),e},p=function(n,e){var f=r(n,s).map(l),y=e||a,p=f[0];if(t(p)===c&&p){var v=[],S=function(n,r,e,f){return function(a){for(var l=o(a),s=l.length,y=0;y<s;y++){var p=l[y],v=a[p];if(v instanceof u){var S=n[+v];t(S)!==c||e.has(S)?a[p]=f.call(a,p,S):(e.add(S),a[p]=i,r.push({o:a,k:p,r:S}))}else a[p]!==i&&(a[p]=f.call(a,p,v))}return a}}(f,v,new Set,y);p=S(p);for(var b=0;b<v.length;){var m=v[b++],g=m.o,h=m.k,O=m.r;g[h]=y.call(g,h,S(O))}}return y.call({"":p},"",p)},v=function(n,r,o){for(var u=r&&t(r)===c?function(n,t){return""===n||-1<r.indexOf(n)?t:void 0}:r||a,i=new Map,l=[],s=[],p=+y(i,l,u.call({"":n},"",n)),v=!p;p<l.length;)v=!0,s[p]=e(l[p++],S,o);return"["+s.join(",")+"]";function S(n,r){if(v)return v=!v,r;var e=u.call(this,n,r);switch(t(e)){case c:if(null===e)return e;case f:return i.get(e)||y(i,l,e)}return e}};return n.fromJSON=function(n){return p(e(n))},n.parse=p,n.stringify=v,n.toJSON=function(n){return r(v(n))},n}({});
\ No newline at end of file
+self.Flatted=function(n){"use strict";function t(n){return t="function"==typeof Symbol&&"symbol"==typeof Symbol.iterator?function(n){return typeof n}:function(n){return n&&"function"==typeof Symbol&&n.constructor===Symbol&&n!==Symbol.prototype?"symbol":typeof n},t(n)}var r=JSON.parse,e=JSON.stringify,o=Object.keys,u=String,i="string",f={},c="object",a=function(n,t){return t},l=function(n){return n instanceof u?u(n):n},s=function(n,r){return t(r)===i?new u(r):r},y=function(n,t,r,e){var o=e.call(n,t,r);void 0===o?delete n[t]:n[t]=o},v=function(n,t,r){var e=u(t.push(r)-1);return n.set(r,e),e},p=function(n,e){var i=r(n,s).map(l),v=e||a,p=i[0];if(t(p)===c&&p){var S=[],b=function(n,r,e,i){return function(a){for(var l=o(a),s=l.length,v=0;v<s;v++){var p=l[v],S=a[p];if(S instanceof u){var b=n[+S];t(b)!==c||e.has(b)?y(a,p,b,i):(e.add(b),a[p]=f,r.push({o:a,k:p,r:b}))}else a[p]!==f&&y(a,p,S,i)}return a}}(i,S,new Set,v);p=b(p);for(var m=0;m<S.length;){var g=S[m++],h=g.o,d=g.k,O=g.r;y(h,d,b(O),v)}}return v.call({"":p},"",p)},S=function(n,r,o){for(var u=r&&t(r)===c?function(n,t){return""===n||-1<r.indexOf(n)?t:void 0}:r||a,f=new Map,l=[],s=[],y=+v(f,l,u.call({"":n},"",n)),p=!y;y<l.length;)p=!0,s[y]=e(l[y++],S,o);return"["+s.join(",")+"]";function S(n,r){if(p)return p=!p,r;var e=u.call(this,n,r);switch(t(e)){case c:if(null===e)return e;case i:return f.get(e)||v(f,l,e)}return e}};return n.fromJSON=function(n){return p(e(n))},n.parse=p,n.stringify=S,n.toJSON=function(n){return r(S(n))},n}({});
\ No newline at end of file
diff --git a/test/index.js b/test/index.js
index 85c18fd..d70a460 100644
--- a/test/index.js
+++ b/test/index.js
@@ -1,4 +1,25 @@
 var Flatted = require('../cjs');
+var assert = require('assert');
+
+var filtered = {number: 1, string: 'keep', removeString: 'drop', nested: {value: 2}, array: [3, 'keep']};
+var removeNumbers = function (key, value) {
+  return typeof value === 'number' || key === 'nested' || key === 'removeString' ? undefined : value;
+};
+assert.deepStrictEqual(
+  Flatted.parse(Flatted.stringify(filtered), removeNumbers),
+  JSON.parse(JSON.stringify(filtered), removeNumbers),
+  'reviver removes object properties and creates array holes'
+);
+
+var filteredCycle = {};
+filteredCycle.self = filteredCycle;
+assert.deepStrictEqual(
+  Flatted.parse(Flatted.stringify(filteredCycle), function (key, value) {
+    return key === 'self' ? undefined : value;
+  }),
+  {},
+  'reviver removes circular reference properties'
+);
 
 console.assert(Flatted.stringify([null, null]) === '[[null,null]]', 'multiple null');