我正在使用nodejs 10.13.0。在终端node --experimental-modules main.mjs上使用命令运行此代码时遇到错误：
(node:3418) ExperimentalWarning: The ESM module loader is experimental.
file:///home/amarjeet/eloquentjs/ch-11%20asynchronous/js/crow-tech.mjs:1
export (function() {
^^^^^^
SyntaxError: Unexpected token export
at translators.set (internal/modules/esm/translators.js:33:13)
这是main.mjs文件：
import {bigOak} from "./crow-tech";
bigOak.readStorage("food caches", caches => {
let firstCache = caches[0];
bigOak.readStorage(firstCache, info => {
console.log(info);
});
});
这是crow-tech.mjs文件：
export (function() {
const connections = [
"Church Tower-Sportsgrounds", "Church Tower-Big Maple", "Big Maple-Sportsgrounds",
"Big Maple-Woods", "Big Maple-Fabienne's Garden", "Fabienne's Garden-Woods",
"Fabienne's Garden-Cow Pasture", "Cow Pasture-Big Oak", "Big Oak-Butcher Shop",
"Butcher Shop-Tall Poplar", "Tall Poplar-Sportsgrounds", "Tall Poplar-Chateau",
"Chateau-Great Pine", "Great Pine-Jaques' Farm", "Jaques' Farm-Hawthorn",
"Great Pine-Hawthorn", "Hawthorn-Gilles' Garden", "Great Pine-Gilles' Garden",
"Gilles' Garden-Big Oak", "Gilles' Garden-Butcher Shop", "Chateau-Butcher Shop"
]
///这只是在js文件中的注释，代码仍在下面，为什么这个问题说导出是未定义的令牌？
function storageFor(name) {
let storage = Object.create(null)
storage["food caches"] = ["cache in the oak", "cache in the meadow", "cache under the hedge"]
storage["cache in the oak"] = "A hollow above the third big branch from the bottom. Several pieces of bread and a pile of acorns."
storage["cache in the meadow"] = "Buried below the patch of nettles (south side). A dead snake."
storage["cache under the hedge"] = "Middle of the hedge at Gilles' garden. Marked with a forked twig. Two bottles of beer."
storage["enemies"] = ["Farmer Jaques' dog", "The butcher", "That one-legged jackdaw", "The boy with the airgun"]
if (name == "Church Tower" || name == "Hawthorn" || name == "Chateau")
storage["events on 2017-12-21"] = "Deep snow. Butcher's garbage can fell over. We chased off the ravens from Saint-Vulbas."
let hash = 0
for (let i = 0; i < name.length; i++) hash += name.charCodeAt(i)
for (let y = 1985; y <= 2018; y++) {
storage[`chicks in ${y}`] = hash % 6
hash = Math.abs((hash << 2) ^ (hash + y))
}
if (name == "Big Oak") storage.scalpel = "Gilles' Garden"
else if (name == "Gilles' Garden") storage.scalpel = "Woods"
else if (name == "Woods") storage.scalpel = "Chateau"
else if (name == "Chateau" || name == "Butcher Shop") storage.scalpel = "Butcher Shop"
else storage.scalpel = "Big Oak"
for (let prop of Object.keys(storage)) storage[prop] = JSON.stringify(storage[prop])
return storage
}
class Network {
constructor(connections, storageFor) {
let reachable = Object.create(null)
for (let [from, to] of connections.map(conn => conn.split("-"))) {
;(reachable[from] || (reachable[from] = [])).push(to)
;(reachable[to] || (reachable[to] = [])).push(from)
}
this.nodes = Object.create(null)
for (let name of Object.keys(reachable))
this.nodes[name] = new Node(name, reachable[name], this, storageFor(name))
this.types = Object.create(null)
}
defineRequestType(name, handler) {
this.types[name] = handler
}
everywhere(f) {
for (let node of Object.values(this.nodes)) f(node)
}
}
const $storage = Symbol("storage"), $network = Symbol("network")
function ser(value) {
return value == null ? null : JSON.parse(JSON.stringify(value))
}
class Node {
constructor(name, neighbors, network, storage) {
this.name = name
this.neighbors = neighbors
this[$network] = network
this.state = Object.create(null)
this[$storage] = storage
}
send(to, type, message, callback) {
let toNode = this[$network].nodes[to]
if (!toNode || !this.neighbors.includes(to))
return callback(new Error(`${to} is not reachable from ${this.name}`))
let handler = this[$network].types[type]
if (!handler)
return callback(new Error("Unknown request type " + type))
if (Math.random() > 0.03) setTimeout(() => {
try {
handler(toNode, ser(message), this.name, (error, response) => {
setTimeout(() => callback(error, ser(response)), 10)
})
} catch(e) {
callback(e)
}
}, 10 * Math.floor(Math.random() * 10))
}
readStorage(name, callback) {
let value = this[$storage][name]
setTimeout(() => callback(value && JSON.parse(value)), 20)
}
writeStorage(name, value, callback) {
setTimeout(() => {
this[$storage][name] = JSON.stringify(value)
callback()
}, 20)
}
}
let network = new Network(connections, storageFor)
exports.bigOak = network.nodes["Big Oak"]
exports.everywhere = network.everywhere.bind(network)
exports.defineRequestType = network.defineRequestType.bind(network)
if (typeof __sandbox != "undefined") {
__sandbox.handleDeps = false
__sandbox.notify.onLoad = () => {
// Kludge to make sure some functions are delayed until the
// nodes have been running for 500ms, to give them a chance to
// propagate network information.
let waitFor = Date.now() + 500
function wrapWaiting(f) {
return function(...args) {
let wait = waitFor - Date.now()
if (wait <= 0) return f(...args)
return new Promise(ok => setTimeout(ok, wait)).then(() => f(...args))
}
}
for (let n of ["routeRequest", "findInStorage", "chicks"])
window[n] = wrapWaiting(window[n])
}
}
if (typeof window != "undefined") {
window.require = name => {
if (name != "./crow-tech") throw new Error("Crow nests can only require \"./crow-tech\"")
return exports
}
} else if (typeof module != "undefined" && module.exports) {
module.exports = exports
}
})()
我不明白我在做什么错！我错了！ 我已经尝试了好几个小时，但仍未解决任何问题，请帮助我！
答案 0 :(得分：0)
您只能导出带有名称的东西，IIFE没有名称：
export const connections = [
"Church Tower-Sportsgrounds", "Church Tower-Big Maple", "Big Maple-Sportsgrounds",
"Big Maple-Woods", "Big Maple-Fabienne's Garden", "Fabienne's Garden-Woods",
"Fabienne's Garden-Cow Pasture", "Cow Pasture-Big Oak", "Big Oak-Butcher Shop",
"Butcher Shop-Tall Poplar", "Tall Poplar-Sportsgrounds", "Tall Poplar-Chateau",
"Chateau-Great Pine", "Great Pine-Jaques' Farm", "Jaques' Farm-Hawthorn",
"Great Pine-Hawthorn", "Hawthorn-Gilles' Garden", "Great Pine-Gilles' Garden",
"Gilles' Garden-Big Oak", "Gilles' Garden-Butcher Shop", "Chateau-Butcher Shop"
];