javascript - 导入的常量未定义

Question

我有一个server.js文件和 main.js编译的文件 watchify app/src/main.js --node -t babelify -o app/build/main.js & watchify app/src/server.js --node -t babelify -o app/build/server.js

main.js:

const rnd = 3

export { rnd }

服务器.js:

import { rnd } from '../build/main'

console.log(rnd)

import express from 'express'

let app = express()

app.listen(8080)

但它记录 undefined 。我做错了什么？

main.js 构建:

(function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
var rnd = 3;

exports.rnd = rnd;

},{}]},{},[1]);

server.js 构建:

(function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
"use strict";

(function e(t, n, r) {
  function s(o, u) {
    if (!n[o]) {
      if (!t[o]) {
        var a = typeof require == "function" && require;if (!u && a) return a(o, !0);if (i) return i(o, !0);var f = new Error("Cannot find module '" + o + "'");throw f.code = "MODULE_NOT_FOUND", f;
      }var l = n[o] = { exports: {} };t[o][0].call(l.exports, function (e) {
        var n = t[o][1][e];return s(n ? n : e);
      }, l, l.exports, e, t, n, r);
    }return n[o].exports;
  }var i = typeof require == "function" && require;for (var o = 0; o < r.length; o++) {
    s(r[o]);
  }return s;
})({ 1: [function (require, module, exports) {
    "use strict";

    Object.defineProperty(exports, "__esModule", {
      value: true
    });
    var rnd = 3;

    exports.rnd = rnd;
  }, {}] }, {}, [1]);

},{}],2:[function(require,module,exports){
'use strict';

var _main = require('../build/main');

var _express = require('express');

var _express2 = _interopRequireDefault(_express);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

console.log(_main.rnd);

var app = (0, _express2.default)();

app.listen(8080);

},{"../build/main":1,"express":20}],3:[function(require,module,exports){

// ...

Answer 1

在 server.js 中，您应该从 app/src/main.js

导入

import { rnd } from 'main'

使用 babelify 编写代码，就像您的环境中拥有所有 ES2015 功能一样(但最好时常检查兼容性表)