objectAssign

A vendorable Object.assign polyfill bundle based on the current object.assign package logic, with helper packages folded into one file for Node.js and Bun use.

Why copy this?

This page ships an Object.assign polyfill bundle based on the current package line, with helper packages folded into a single vendorable file. The value is to keep assign semantics local without carrying a larger helper graph.

Native alternative: Object.assign exists in modern runtimes, but teams cleaning up old compatibility helpers may still want a vendorable shim with the familiar export shape.

Note: Current object.assign releases depend on multiple helper packages. This snippet folds those helpers into one vendorable file for a practical first pass.

This copy is your responsibility once you adopt it. It does not automatically receive upstream bug fixes or security updates.

Snippet

Copy-first distribution

Normalized

ESM / TS / normalized

Runtime: node, bun

/**
 * Derived from [email protected]
 * Rule-based normalized variant generated by this repository.
 * Preserve the upstream license and attribution notices when copying this file.
 */
/**
 * Derived from [email protected]
 * Rule-based normalized variant generated by this repository.
 * See THIRD_PARTY_NOTICES.md for upstream license and attribution details.
 */
"use strict";
var objectKeys = Object.keys;
var $Object = Object;
var $push = Function.call.bind(Array.prototype.push);
var $propIsEnumerable = Function.call.bind(Object.prototype.propertyIsEnumerable);

function hasSymbols() {
  if (typeof Symbol !== "function" || typeof Object.getOwnPropertySymbols !== "function") {
    return false;
  }
  if (typeof Symbol.iterator === "symbol") {
    return true;
  }

  var obj = {};
  var sym = Symbol("test");
  var symObj = Object(sym);
  if (typeof sym === "string") {
    return false;
  }

  if (Object.prototype.toString.call(sym) !== "[object Symbol]") {
    return false;
  }
  if (Object.prototype.toString.call(symObj) !== "[object Symbol]") {
    return false;
  }

  var symVal = 42;
  obj[sym] = symVal;
  for (sym in obj) {
    return false;
  }
  if (objectKeys(obj).length !== 0) {
    return false;
  }
  if (
    typeof Object.getOwnPropertyNames === "function" &&
    Object.getOwnPropertyNames(obj).length !== 0
  ) {
    return false;
  }

  var syms = Object.getOwnPropertySymbols(obj);
  if (syms.length !== 1 || syms[0] !== sym) {
    return false;
  }

  if (!Object.prototype.propertyIsEnumerable.call(obj, sym)) {
    return false;
  }

  if (typeof Object.getOwnPropertyDescriptor === "function") {
    var descriptor = Object.getOwnPropertyDescriptor(obj, sym);
    if (descriptor.value !== symVal || descriptor.enumerable !== true) {
      return false;
    }
  }

  return true;
}

var implementation = function assign(target, source1) {
  if (target == null) {
    throw new TypeError("target must be an object");
  }
  var to = $Object(target);
  if (arguments.length === 1) {
    return to;
  }
  for (var s = 1; s < arguments.length; ++s) {
    var from = $Object(arguments[s]);
    var keys = objectKeys(from);
    var getSymbols = hasSymbols() && $Object.getOwnPropertySymbols;
    if (getSymbols) {
      var syms = getSymbols(from);
      for (var j = 0; j < syms.length; ++j) {
        var key = syms[j];
        if ($propIsEnumerable(from, key)) {
          $push(keys, key);
        }
      }
    }

    for (var i = 0; i < keys.length; ++i) {
      var nextKey = keys[i];
      if ($propIsEnumerable(from, nextKey)) {
        var propValue = from[nextKey];
        to[nextKey] = propValue;
      }
    }
  }

  return to;
};

var lacksProperEnumerationOrder = function () {
  if (!Object.assign) {
    return false;
  }
  var str = "abcdefghijklmnopqrst";
  var letters = str.split("");
  var map = {};
  for (var i = 0; i < letters.length; ++i) {
    map[letters[i]] = letters[i];
  }
  var obj = Object.assign({}, map);
  var actual = "";
  for (var k in obj) {
    actual += k;
  }
  return str !== actual;
};

var assignHasPendingExceptions = function () {
  if (!Object.assign || !Object.preventExtensions) {
    return false;
  }
  var thrower = Object.preventExtensions({ 1: 2 });
  try {
    Object.assign(thrower, "xy");
  } catch (e) {
    return thrower[1] === "y";
  }
  return false;
};

var getPolyfill = function getPolyfill() {
  if (!Object.assign) {
    return implementation;
  }
  if (lacksProperEnumerationOrder()) {
    return implementation;
  }
  if (assignHasPendingExceptions()) {
    return implementation;
  }
  return Object.assign;
};

var shim = function shimAssign() {
  var polyfill = getPolyfill();
  if (typeof Object.defineProperty === "function") {
    Object.defineProperty(Object, "assign", {
      configurable: true,
      enumerable: false,
      writable: true,
      value: polyfill,
    });
  } else {
    Object.assign = polyfill;
  }
  return polyfill;
};

var polyfill = getPolyfill();
var bound = function assign(target, source1) {
  return polyfill.apply(Object, arguments);
};

if (typeof Object.defineProperty === "function") {
  Object.defineProperty(bound, "getPolyfill", {
    configurable: true,
    enumerable: false,
    writable: true,
    value: getPolyfill,
  });
  Object.defineProperty(bound, "implementation", {
    configurable: true,
    enumerable: false,
    writable: true,
    value: implementation,
  });
  Object.defineProperty(bound, "shim", {
    configurable: true,
    enumerable: false,
    writable: true,
    value: shim,
  });
} else {
  bound.getPolyfill = getPolyfill;
  bound.implementation = implementation;
  bound.shim = shim;
}

export default bound;

Variant note: Bundled into one file and then rule-based normalized for copy-paste into modern TS projects.

Transforms: module.exports-to-export-default, js-extension-to-ts-extension, bundled-upstream-helper

Validation: This normalized variant is intended to stay oxlint and oxfmt clean in this repo.

Raw

CJS / JS / raw

Runtime: node, bun

'use strict';

var objectKeys = Object.keys;
var $Object = Object;
var $push = Function.call.bind(Array.prototype.push);
var $propIsEnumerable = Function.call.bind(Object.prototype.propertyIsEnumerable);

function hasSymbols() {
  if (typeof Symbol !== 'function' || typeof Object.getOwnPropertySymbols !== 'function') {
    return false;
  }
  if (typeof Symbol.iterator === 'symbol') {
    return true;
  }

  var obj = {};
  var sym = Symbol('test');
  var symObj = Object(sym);
  if (typeof sym === 'string') {
    return false;
  }

  if (Object.prototype.toString.call(sym) !== '[object Symbol]') {
    return false;
  }
  if (Object.prototype.toString.call(symObj) !== '[object Symbol]') {
    return false;
  }

  var symVal = 42;
  obj[sym] = symVal;
  for (sym in obj) {
    return false;
  }
  if (objectKeys(obj).length !== 0) {
    return false;
  }
  if (typeof Object.getOwnPropertyNames === 'function' && Object.getOwnPropertyNames(obj).length !== 0) {
    return false;
  }

  var syms = Object.getOwnPropertySymbols(obj);
  if (syms.length !== 1 || syms[0] !== sym) {
    return false;
  }

  if (!Object.prototype.propertyIsEnumerable.call(obj, sym)) {
    return false;
  }

  if (typeof Object.getOwnPropertyDescriptor === 'function') {
    var descriptor = Object.getOwnPropertyDescriptor(obj, sym);
    if (descriptor.value !== symVal || descriptor.enumerable !== true) {
      return false;
    }
  }

  return true;
}

var implementation = function assign(target, source1) {
  if (target == null) {
    throw new TypeError('target must be an object');
  }
  var to = $Object(target);
  if (arguments.length === 1) {
    return to;
  }
  for (var s = 1; s < arguments.length; ++s) {
    var from = $Object(arguments[s]);
    var keys = objectKeys(from);
    var getSymbols = hasSymbols() && $Object.getOwnPropertySymbols;
    if (getSymbols) {
      var syms = getSymbols(from);
      for (var j = 0; j < syms.length; ++j) {
        var key = syms[j];
        if ($propIsEnumerable(from, key)) {
          $push(keys, key);
        }
      }
    }

    for (var i = 0; i < keys.length; ++i) {
      var nextKey = keys[i];
      if ($propIsEnumerable(from, nextKey)) {
        var propValue = from[nextKey];
        to[nextKey] = propValue;
      }
    }
  }

  return to;
};

var lacksProperEnumerationOrder = function () {
  if (!Object.assign) {
    return false;
  }
  var str = 'abcdefghijklmnopqrst';
  var letters = str.split('');
  var map = {};
  for (var i = 0; i < letters.length; ++i) {
    map[letters[i]] = letters[i];
  }
  var obj = Object.assign({}, map);
  var actual = '';
  for (var k in obj) {
    actual += k;
  }
  return str !== actual;
};

var assignHasPendingExceptions = function () {
  if (!Object.assign || !Object.preventExtensions) {
    return false;
  }
  var thrower = Object.preventExtensions({ 1: 2 });
  try {
    Object.assign(thrower, 'xy');
  } catch (e) {
    return thrower[1] === 'y';
  }
  return false;
};

var getPolyfill = function getPolyfill() {
  if (!Object.assign) {
    return implementation;
  }
  if (lacksProperEnumerationOrder()) {
    return implementation;
  }
  if (assignHasPendingExceptions()) {
    return implementation;
  }
  return Object.assign;
};

var shim = function shimAssign() {
  var polyfill = getPolyfill();
  if (typeof Object.defineProperty === 'function') {
    Object.defineProperty(Object, 'assign', {
      configurable: true,
      enumerable: false,
      writable: true,
      value: polyfill
    });
  } else {
    Object.assign = polyfill;
  }
  return polyfill;
};

var polyfill = getPolyfill();
var bound = function assign(target, source1) {
  return polyfill.apply(Object, arguments);
};

if (typeof Object.defineProperty === 'function') {
  Object.defineProperty(bound, 'getPolyfill', {
    configurable: true,
    enumerable: false,
    writable: true,
    value: getPolyfill
  });
  Object.defineProperty(bound, 'implementation', {
    configurable: true,
    enumerable: false,
    writable: true,
    value: implementation
  });
  Object.defineProperty(bound, 'shim', {
    configurable: true,
    enumerable: false,
    writable: true,
    value: shim
  });
} else {
  bound.getPolyfill = getPolyfill;
  bound.implementation = implementation;
  bound.shim = shim;
}

module.exports = bound;

Variant note: Single-file CommonJS bundle preserving the package's bound export shape and helper methods.