I am developing a set of reusable components and I am getting the error React.createElement: type is invalid -- expected a string (for built-in components) or a class/function (for composite components) but got: undefined. You likely forgot to export your component from the file it's defined in, or you might have mixed up default and named imports. after bundling and importing to another react compoponent as follows,
import Label from 'path/to/bundle/dist/Label';
I tried importing the unbundled component in the src folder (the Label component as shown below) by providing the path and it works fine. As soon as I bundle, and point to the bundled file it throws the above error.
Any help what maybe causing this is much apprecated!
The code base for, the bundled/unbundled component, webpack config, babelrc and devdependencies for babel and webpack are listed below.
NOTE: this is a package with a multiple entry points. if this info makes any difference :)
The implementation of the reusable component (Label) is as follows,
import React from 'react';
import PropTypes from 'prop-types';
const Label = (props) => {
const {
id,
className,
children,
...other
} = props;
return (
<label id={id} className={className} {...other}>{children}</label>
);
};
export default Label;
Label.propTypes = {
id: PropTypes.string,
className: PropTypes.string,
children: PropTypes.node,
};
Label.defaultProps = {
id: '',
className: '',
children: null,
};
the .babelrc file,
{
"presets": ["es2015", "env", "react", "stage-2"],
"plugins": ["transform-es2015-arrow-functions", "check-es2015-constants", "transform-es2015-block-scoping"]
}
the wbepack.config.js file
const path = require('path');
const CleanWebpackPlugin = require('clean-webpack-plugin');
const fs = require('fs');
module.exports = {
entry: {
Label: 'path/to/Label',
Button: 'path/to/Button',
},
output: {
path: path.join(__dirname, 'dist'),
filename: '[name]/index.js',
},
optimization:{
minimize: false,
},
module: {
rules: [
{
test: /\.(js|jsx)$/,
exclude: /node_modules/,
loader: 'babel-loader',
},
{
test: /\.(svg|jpe?g|png|gif)$/,
use: {
loader: 'file-loader',
options: {
emitFile: false,
name: '[path][name].[ext]',
},
},
},
],
},
plugins: [new CleanWebpackPlugin()],
};
the babel and webpack devDependencies,
"babel-loader": "^7.1.4",
"babel-plugin-check-es2015-constants": "^6.22.0",
"babel-plugin-transform-es2015-arrow-functions": "^6.22.0",
"babel-plugin-transform-es2015-block-scoping": "^6.26.0",
"babel-preset-env": "^1.7.0",
"babel-preset-es2015": "^6.24.1",
"babel-preset-react": "^6.24.1",
"babel-preset-stage-2": "^6.24.1",
"webpack": "^4.30.0",
"webpack-cli": "^3.3.1"
the code after bundling is as follows,
/******/ (function(modules) { // webpackBootstrap
/******/ // The module cache
/******/ var installedModules = {};
/******/
/******/ // The require function
/******/ function __webpack_require__(moduleId) {
/******/
/******/ // Check if module is in cache
/******/ if(installedModules[moduleId]) {
/******/ return installedModules[moduleId].exports;
/******/ }
/******/ // Create a new module (and put it into the cache)
/******/ var module = installedModules[moduleId] = {
/******/ i: moduleId,
/******/ l: false,
/******/ exports: {}
/******/ };
/******/
/******/ // Execute the module function
/******/ modules[moduleId].call(module.exports, module, module.exports, __webpack_require__);
/******/
/******/ // Flag the module as loaded
/******/ module.l = true;
/******/
/******/ // Return the exports of the module
/******/ return module.exports;
/******/ }
/******/
/******/
/******/ // expose the modules object (__webpack_modules__)
/******/ __webpack_require__.m = modules;
/******/
/******/ // expose the module cache
/******/ __webpack_require__.c = installedModules;
/******/
/******/ // define getter function for harmony exports
/******/ __webpack_require__.d = function(exports, name, getter) {
/******/ if(!__webpack_require__.o(exports, name)) {
/******/ Object.defineProperty(exports, name, { enumerable: true, get: getter });
/******/ }
/******/ };
/******/
/******/ // define __esModule on exports
/******/ __webpack_require__.r = function(exports) {
/******/ if(typeof Symbol !== 'undefined' && Symbol.toStringTag) {
/******/ Object.defineProperty(exports, Symbol.toStringTag, { value: 'Module' });
/******/ }
/******/ Object.defineProperty(exports, '__esModule', { value: true });
/******/ };
/******/
/******/ // create a fake namespace object
/******/ // mode & 1: value is a module id, require it
/******/ // mode & 2: merge all properties of value into the ns
/******/ // mode & 4: return value when already ns object
/******/ // mode & 8|1: behave like require
/******/ __webpack_require__.t = function(value, mode) {
/******/ if(mode & 1) value = __webpack_require__(value);
/******/ if(mode & 8) return value;
/******/ if((mode & 4) && typeof value === 'object' && value && value.__esModule) return value;
/******/ var ns = Object.create(null);
/******/ __webpack_require__.r(ns);
/******/ Object.defineProperty(ns, 'default', { enumerable: true, value: value });
/******/ if(mode & 2 && typeof value != 'string') for(var key in value) __webpack_require__.d(ns, key, function(key) { return value[key]; }.bind(null, key));
/******/ return ns;
/******/ };
/******/
/******/ // getDefaultExport function for compatibility with non-harmony modules
/******/ __webpack_require__.n = function(module) {
/******/ var getter = module && module.__esModule ?
/******/ function getDefault() { return module['default']; } :
/******/ function getModuleExports() { return module; };
/******/ __webpack_require__.d(getter, 'a', getter);
/******/ return getter;
/******/ };
/******/
/******/ // Object.prototype.hasOwnProperty.call
/******/ __webpack_require__.o = function(object, property) { return Object.prototype.hasOwnProperty.call(object, property); };
/******/
/******/ // __webpack_public_path__
/******/ __webpack_require__.p = "";
/******/
/******/
/******/ // Load entry module and return exports
/******/ return __webpack_require__(__webpack_require__.s = 8);
/******/ })
/************************************************************************/
/******/ ([
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/**
* Copyright (c) 2013-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
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*/
if (false) { var throwOnDirectAccess, ReactIs; } else {
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*
* Copyright (c) Facebook, Inc. and its affiliates.
*
* This source code is licensed under the MIT license found in the
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*/
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/***/ (function(module, exports, __webpack_require__) {
"use strict";
/*
object-assign
(c) Sindre Sorhus
@license MIT
*/
/* eslint-disable no-unused-vars */
var getOwnPropertySymbols = Object.getOwnPropertySymbols;
var hasOwnProperty = Object.prototype.hasOwnProperty;
var propIsEnumerable = Object.prototype.propertyIsEnumerable;
function toObject(val) {
if (val === null || val === undefined) {
throw new TypeError('Object.assign cannot be called with null or undefined');
}
return Object(val);
}
function shouldUseNative() {
try {
if (!Object.assign) {
return false;
}
// Detect buggy property enumeration order in older V8 versions.
// https://bugs.chromium.org/p/v8/issues/detail?id=4118
var test1 = new String('abc'); // eslint-disable-line no-new-wrappers
test1[5] = 'de';
if (Object.getOwnPropertyNames(test1)[0] === '5') {
return false;
}
// https://bugs.chromium.org/p/v8/issues/detail?id=3056
var test2 = {};
for (var i = 0; i < 10; i++) {
test2['_' + String.fromCharCode(i)] = i;
}
var order2 = Object.getOwnPropertyNames(test2).map(function (n) {
return test2[n];
});
if (order2.join('') !== '0123456789') {
return false;
}
// https://bugs.chromium.org/p/v8/issues/detail?id=3056
var test3 = {};
'abcdefghijklmnopqrst'.split('').forEach(function (letter) {
test3[letter] = letter;
});
if (Object.keys(Object.assign({}, test3)).join('') !==
'abcdefghijklmnopqrst') {
return false;
}
return true;
} catch (err) {
// We don't expect any of the above to throw, but better to be safe.
return false;
}
}
module.exports = shouldUseNative() ? Object.assign : function (target, source) {
var from;
var to = toObject(target);
var symbols;
for (var s = 1; s < arguments.length; s++) {
from = Object(arguments[s]);
for (var key in from) {
if (hasOwnProperty.call(from, key)) {
to[key] = from[key];
}
}
if (getOwnPropertySymbols) {
symbols = getOwnPropertySymbols(from);
for (var i = 0; i < symbols.length; i++) {
if (propIsEnumerable.call(from, symbols[i])) {
to[symbols[i]] = from[symbols[i]];
}
}
}
}
return to;
};
/***/ }),
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/***/ (function(module, exports, __webpack_require__) {
"use strict";
/**
* Copyright (c) 2013-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
var ReactPropTypesSecret = __webpack_require__(5);
function emptyFunction() {}
function emptyFunctionWithReset() {}
emptyFunctionWithReset.resetWarningCache = emptyFunction;
module.exports = function() {
function shim(props, propName, componentName, location, propFullName, secret) {
if (secret === ReactPropTypesSecret) {
// It is still safe when called from React.
return;
}
var err = new Error(
'Calling PropTypes validators directly is not supported by the `prop-types` package. ' +
'Use PropTypes.checkPropTypes() to call them. ' +
'Read more at'
);
err.name = 'Invariant Violation';
throw err;
};
shim.isRequired = shim;
function getShim() {
return shim;
};
// Important!
// Keep this list in sync with production version in `./factoryWithTypeCheckers.js`.
var ReactPropTypes = {
array: shim,
bool: shim,
func: shim,
number: shim,
object: shim,
string: shim,
symbol: shim,
any: shim,
arrayOf: getShim,
element: shim,
elementType: shim,
instanceOf: getShim,
node: shim,
objectOf: getShim,
oneOf: getShim,
oneOfType: getShim,
shape: getShim,
exact: getShim,
checkPropTypes: emptyFunctionWithReset,
resetWarningCache: emptyFunction
};
ReactPropTypes.PropTypes = ReactPropTypes;
return ReactPropTypes;
};
/***/ }),
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/***/ (function(module, exports, __webpack_require__) {
"use strict";
/**
* Copyright (c) 2013-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
var ReactPropTypesSecret = 'SECRET_DO_NOT_PASS_THIS_OR_YOU_WILL_BE_FIRED';
module.exports = ReactPropTypesSecret;
/***/ }),
/* 6 */,
/* 7 */,
/* 8 */
/***/ (function(module, exports, __webpack_require__) {
"use strict";
Object.defineProperty(exports, "__esModule", {
value: true
});
var _extends = Object.assign || function (target) { for (var i = 1; i < arguments.length; i++) { var source = arguments[i]; for (var key in source) { if (Object.prototype.hasOwnProperty.call(source, key)) { target[key] = source[key]; } } } return target; };
var _react = __webpack_require__(0);
var _react2 = _interopRequireDefault(_react);
var _propTypes = __webpack_require__(1);
var _propTypes2 = _interopRequireDefault(_propTypes);
function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
function _objectWithoutProperties(obj, keys) { var target = {}; for (var i in obj) { if (keys.indexOf(i) >= 0) continue; if (!Object.prototype.hasOwnProperty.call(obj, i)) continue; target[i] = obj[i]; } return target; }
var Label = function Label(props) {
var id = props.id,
className = props.className,
children = props.children,
other = _objectWithoutProperties(props, ['id', 'className', 'children']);
return _react2.default.createElement(
'label',
_extends({ id: id, className: className }, other),
children
);
};
exports.default = Label;
Label.propTypes = {
id: _propTypes2.default.string,
className: _propTypes2.default.string,
children: _propTypes2.default.node
};
Label.defaultProps = {
id: '',
className: '',
children: null
};
/***/ })
/******/ ]);
Found an answer by Michael Jungo in a similar question: https://stackoverflow.com/a/44542254/4513747
A webpack bundle does not expose your exports by default, as it assumes that you're building an app and not a library (which is the far more common use of webpack). You can create a library by configuring
output.libraryandoutput.libraryTarget
The documentation at https://webpack.js.org/guides/author-libraries, walks you through the process of using webpack for bundling a library.
Using the output in webpack.config.js as in the following, exposes the exports when bundling.
output: {
path: path.join(__dirname, 'dist'),
filename: '[name]/index.js',
library: 'yourLibraryName',
libraryTarget: 'umd',
},
More information on this can be found at https://webpack.js.org/configuration/output/#output-library