我正在开发一套可重复使用的组件，并且按照如下所示捆绑并导入到另一个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.支持者中后出现错误react，
import Label from 'path/to/bundle/dist/Label';
我尝试通过提供路径将未捆绑的组件导入src文件夹（如下所示的Label组件）中，并且工作正常。一旦我捆绑并指向捆绑的文件，它将引发以上错误。
任何帮助可能导致这种情况的方法都深表感谢！
下面列出了代码库，捆绑/解除捆绑的组件，webpack配置，babelrc以及babel和webpack的偏差。
注意：这是一个具有多个入口点的软件包。如果此信息有任何不同：）
可重用组件（Label）的实现如下，
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,
};
.babelrc文件，
{
"presets": ["es2015", "env", "react", "stage-2"],
"plugins": ["transform-es2015-arrow-functions", "check-es2015-constants", "transform-es2015-block-scoping"]
}
wbepack.config.js文件
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()],
};
babel和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"
捆绑后的代码如下，
/******/ (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);
/******/ })
/************************************************************************/
/******/ ([
/* 0 */
/***/ (function(module, exports, __webpack_require__) {
"use strict";
if (true) {
module.exports = __webpack_require__(2);
} else {}
/***/ }),
/* 1 */
/***/ (function(module, exports, __webpack_require__) {
/**
* 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.
*/
if (false) { var throwOnDirectAccess, ReactIs; } else {
// By explicitly using `prop-types` you are opting into new production behavior.
module.exports = __webpack_require__(4)();
}
/***/ }),
/* 2 */
/***/ (function(module, exports, __webpack_require__) {
"use strict";
/** @license React v16.8.6
* react.production.min.js
*
* Copyright (c) Facebook, Inc. and its affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
var k=__webpack_require__(3),n="function"===typeof Symbol&&Symbol.for,p=n?Symbol.for("react.element"):60103,q=n?Symbol.for("react.portal"):60106,r=n?Symbol.for("react.fragment"):60107,t=n?Symbol.for("react.strict_mode"):60108,u=n?Symbol.for("react.profiler"):60114,v=n?Symbol.for("react.provider"):60109,w=n?Symbol.for("react.context"):60110,x=n?Symbol.for("react.concurrent_mode"):60111,y=n?Symbol.for("react.forward_ref"):60112,z=n?Symbol.for("react.suspense"):60113,aa=n?Symbol.for("react.memo"):
60115,ba=n?Symbol.for("react.lazy"):60116,A="function"===typeof Symbol&&Symbol.iterator;function ca(a,b,d,c,e,g,h,f){if(!a){a=void 0;if(void 0===b)a=Error("Minified exception occurred; use the non-minified dev environment for the full error message and additional helpful warnings.");else{var l=[d,c,e,g,h,f],m=0;a=Error(b.replace(/%s/g,function(){return l[m++]}));a.name="Invariant Violation"}a.framesToPop=1;throw a;}}
function B(a){for(var b=arguments.length-1,d="https://reactjs.org/docs/error-decoder.html?invariant="+a,c=0;c<b;c++)d+="&args[]="+encodeURIComponent(arguments[c+1]);ca(!1,"Minified React error #"+a+"; visit %s for the full message or use the non-minified dev environment for full errors and additional helpful warnings. ",d)}var C={isMounted:function(){return!1},enqueueForceUpdate:function(){},enqueueReplaceState:function(){},enqueueSetState:function(){}},D={};
function E(a,b,d){this.props=a;this.context=b;this.refs=D;this.updater=d||C}E.prototype.isReactComponent={};E.prototype.setState=function(a,b){"object"!==typeof a&&"function"!==typeof a&&null!=a?B("85"):void 0;this.updater.enqueueSetState(this,a,b,"setState")};E.prototype.forceUpdate=function(a){this.updater.enqueueForceUpdate(this,a,"forceUpdate")};function F(){}F.prototype=E.prototype;function G(a,b,d){this.props=a;this.context=b;this.refs=D;this.updater=d||C}var H=G.prototype=new F;
H.constructor=G;k(H,E.prototype);H.isPureReactComponent=!0;var I={current:null},J={current:null},K=Object.prototype.hasOwnProperty,L={key:!0,ref:!0,__self:!0,__source:!0};
function M(a,b,d){var c=void 0,e={},g=null,h=null;if(null!=b)for(c in void 0!==b.ref&&(h=b.ref),void 0!==b.key&&(g=""+b.key),b)K.call(b,c)&&!L.hasOwnProperty(c)&&(e[c]=b[c]);var f=arguments.length-2;if(1===f)e.children=d;else if(1<f){for(var l=Array(f),m=0;m<f;m++)l[m]=arguments[m+2];e.children=l}if(a&&a.defaultProps)for(c in f=a.defaultProps,f)void 0===e[c]&&(e[c]=f[c]);return{$$typeof:p,type:a,key:g,ref:h,props:e,_owner:J.current}}
function da(a,b){return{$$typeof:p,type:a.type,key:b,ref:a.ref,props:a.props,_owner:a._owner}}function N(a){return"object"===typeof a&&null!==a&&a.$$typeof===p}function escape(a){var b={"=":"=0",":":"=2"};return"$"+(""+a).replace(/[=:]/g,function(a){return b[a]})}var O=/\/+/g,P=[];function Q(a,b,d,c){if(P.length){var e=P.pop();e.result=a;e.keyPrefix=b;e.func=d;e.context=c;e.count=0;return e}return{result:a,keyPrefix:b,func:d,context:c,count:0}}
function R(a){a.result=null;a.keyPrefix=null;a.func=null;a.context=null;a.count=0;10>P.length&&P.push(a)}
function S(a,b,d,c){var e=typeof a;if("undefined"===e||"boolean"===e)a=null;var g=!1;if(null===a)g=!0;else switch(e){case "string":case "number":g=!0;break;case "object":switch(a.$$typeof){case p:case q:g=!0}}if(g)return d(c,a,""===b?"."+T(a,0):b),1;g=0;b=""===b?".":b+":";if(Array.isArray(a))for(var h=0;h<a.length;h++){e=a[h];var f=b+T(e,h);g+=S(e,f,d,c)}else if(null===a||"object"!==typeof a?f=null:(f=A&&a[A]||a["@@iterator"],f="function"===typeof f?f:null),"function"===typeof f)for(a=f.call(a),h=
0;!(e=a.next()).done;)e=e.value,f=b+T(e,h++),g+=S(e,f,d,c);else"object"===e&&(d=""+a,B("31","[object Object]"===d?"object with keys {"+Object.keys(a).join(", ")+"}":d,""));return g}function U(a,b,d){return null==a?0:S(a,"",b,d)}function T(a,b){return"object"===typeof a&&null!==a&&null!=a.key?escape(a.key):b.toString(36)}function ea(a,b){a.func.call(a.context,b,a.count++)}
function fa(a,b,d){var c=a.result,e=a.keyPrefix;a=a.func.call(a.context,b,a.count++);Array.isArray(a)?V(a,c,d,function(a){return a}):null!=a&&(N(a)&&(a=da(a,e+(!a.key||b&&b.key===a.key?"":(""+a.key).replace(O,"$&/")+"/")+d)),c.push(a))}function V(a,b,d,c,e){var g="";null!=d&&(g=(""+d).replace(O,"$&/")+"/");b=Q(b,g,c,e);U(a,fa,b);R(b)}function W(){var a=I.current;null===a?B("321"):void 0;return a}
var X={Children:{map:function(a,b,d){if(null==a)return a;var c=[];V(a,c,null,b,d);return c},forEach:function(a,b,d){if(null==a)return a;b=Q(null,null,b,d);U(a,ea,b);R(b)},count:function(a){return U(a,function(){return null},null)},toArray:function(a){var b=[];V(a,b,null,function(a){return a});return b},only:function(a){N(a)?void 0:B("143");return a}},createRef:function(){return{current:null}},Component:E,PureComponent:G,createContext:function(a,b){void 0===b&&(b=null);a={$$typeof:w,_calculateChangedBits:b,
_currentValue:a,_currentValue2:a,_threadCount:0,Provider:null,Consumer:null};a.Provider={$$typeof:v,_context:a};return a.Consumer=a},forwardRef:function(a){return{$$typeof:y,render:a}},lazy:function(a){return{$$typeof:ba,_ctor:a,_status:-1,_result:null}},memo:function(a,b){return{$$typeof:aa,type:a,compare:void 0===b?null:b}},useCallback:function(a,b){return W().useCallback(a,b)},useContext:function(a,b){return W().useContext(a,b)},useEffect:function(a,b){return W().useEffect(a,b)},useImperativeHandle:function(a,
b,d){return W().useImperativeHandle(a,b,d)},useDebugValue:function(){},useLayoutEffect:function(a,b){return W().useLayoutEffect(a,b)},useMemo:function(a,b){return W().useMemo(a,b)},useReducer:function(a,b,d){return W().useReducer(a,b,d)},useRef:function(a){return W().useRef(a)},useState:function(a){return W().useState(a)},Fragment:r,StrictMode:t,Suspense:z,createElement:M,cloneElement:function(a,b,d){null===a||void 0===a?B("267",a):void 0;var c=void 0,e=k({},a.props),g=a.key,h=a.ref,f=a._owner;if(null!=
b){void 0!==b.ref&&(h=b.ref,f=J.current);void 0!==b.key&&(g=""+b.key);var l=void 0;a.type&&a.type.defaultProps&&(l=a.type.defaultProps);for(c in b)K.call(b,c)&&!L.hasOwnProperty(c)&&(e[c]=void 0===b[c]&&void 0!==l?l[c]:b[c])}c=arguments.length-2;if(1===c)e.children=d;else if(1<c){l=Array(c);for(var m=0;m<c;m++)l[m]=arguments[m+2];e.children=l}return{$$typeof:p,type:a.type,key:g,ref:h,props:e,_owner:f}},createFactory:function(a){var b=M.bind(null,a);b.type=a;return b},isValidElement:N,version:"16.8.6",
unstable_ConcurrentMode:x,unstable_Profiler:u,__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED:{ReactCurrentDispatcher:I,ReactCurrentOwner:J,assign:k}},Y={default:X},Z=Y&&X||Y;module.exports=Z.default||Z;
/***/ }),
/* 3 */
/***/ (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;
};
/***/ }),
/* 4 */
/***/ (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;
};
/***/ }),
/* 5 */
/***/ (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
};
/***/ })
/******/ ]);
答案 0 :(得分：1)
找到Michael Jungo的类似问题的答案：https://stackoverflow.com/a/44542254/4513747
默认情况下，Webpack捆绑包不会公开您的导出内容，因为它 假设您正在构建的是应用而不是库（ webpack的用法更为常见）。您可以通过以下方式创建一个库 配置
output.library和output.libraryTarget
https://webpack.js.org/guides/author-libraries上的文档将引导您完成使用webpack捆绑库的过程。
按如下所示使用webpack.config.js中的输出，在捆绑时将显示export。
output: {
path: path.join(__dirname, 'dist'),
filename: '[name]/index.js',
library: 'yourLibraryName',
libraryTarget: 'umd',
},
有关更多信息，请访问https://webpack.js.org/configuration/output/#output-library