Element type is invalid -- expected a string (for built-in components) or a class/function (for composite components) but got undefined

原因就是组件引入错误，应该是

import {BillReverse} form '../xx'

写成了

import Reverse from '../xx'

两个错误

1. 没写大括号

2. 组件名错误

如何从打包后的文件分析导出内容格式

1. 新版的webpack打包umd已经没有webpackUniversalModuleDefinition这个函数名了

(function webpackUniversalModuleDefinition(root, factory){
    // 这里是支持umd规范的写法
})(window, function(){
    // 这里是index.js源码
    //
    ...val: 'hello webpack'\n};\n\nexports.default = webpackDemo;...
})

2. 新版webpack打包umd的格式如下

! function(e, t) {
    "object" == typeof exports && "object" == typeof module ? module.exports = t() : "function" == typeof define && define.amd ? define([], t) : "object" == typeof exports ? exports.lib = t() : e.lib = t()
}(window, (function() {
    return function(e) {
        var t = {};

        function n(r) {
            if (t[r]) return t[r].exports;
            var o = t[r] = {
                i: r,
                l: !1,
                exports: {}
            };
            return e[r].call(o.exports, o, o.exports, n), o.l = !0, o.exports
        }
        return n.m = e, n.c = t, n.d = function(e, t, r) {
            n.o(e, t) || Object.defineProperty(e, t, {
                enumerable: !0,
                get: r
            })
        }, n.r = function(e) {
            "undefined" != typeof Symbol && Symbol.toStringTag && Object.defineProperty(e, Symbol.toStringTag, {
                value: "Module"
            }), Object.defineProperty(e, "__esModule", {
                value: !0
            })
        }, n.t = function(e, t) {
            if (1 & t && (e = n(e)), 8 & t) return e;
            if (4 & t && "object" == typeof e && e && e.__esModule) return e;
            var r = Object.create(null);
            if (n.r(r), Object.defineProperty(r, "default", {
                    enumerable: !0,
                    value: e
                }), 2 & t && "string" != typeof e)
                for (var o in e) n.d(r, o, function(t) {
                    return e[t]
                }.bind(null, o));
            return r
        }, n.n = function(e) {
            var t = e && e.__esModule ? function() {
                return e.default
            } : function() {
                return e
            };
            return n.d(t, "a", t), t
        }, n.o = function(e, t) {
            return Object.prototype.hasOwnProperty.call(e, t)
        }, n.p = "", n(n.s = 0)
    }([function(e, t, n) {
        e.exports = n(1)
    }, function(e, t, n) {
        "use strict";
        n.r(t);
        c = 1 + 2;
        t.default = c
    }])
}));