Javascript TypeError:您只能生成函数、承诺、生成器。。。生成app.listen()时
我无法判断此发电机功能有何问题:Javascript TypeError:您只能生成函数、承诺、生成器。。。生成app.listen()时,javascript,node.js,express,generator,Javascript,Node.js,Express,Generator,我无法判断此发电机功能有何问题: var dbUrl = 'mongodb://localhost:27017/voyanta'; var db; var server; co(function*() { // Use connect method to connect to the Server db = yield MongoClient.connect(dbUrl); server = yield app.listen(3000); console.log
var dbUrl = 'mongodb://localhost:27017/voyanta';
var db;
var server;
co(function*() {
// Use connect method to connect to the Server
db = yield MongoClient.connect(dbUrl);
server = yield app.listen(3000);
console.log('Connected to database. Listening on port 3000.');
}).catch(function(err) {
console.log(err.stack);
});
在我看来,这看起来很好,但是“server=yield app.listen(3000);”这行创建了错误:“Type error:您可能只生成函数、承诺、生成器、数组或对象,但传递了以下对象:“[object object]”。app.listen(3000)
不返回承诺
而不是:
server = yield app.listen(3000);
您可以执行以下操作:
server = app.listen(3000);
yield new Promise(res => server.on('listening', res));
或者更好:
server = app.listen(3000);
yield new Promise((res, rej) => {
server.on('listening', res);
server.on('error', rej);
});
使用此示例进行测试:
var co = require('co');
var app = require('express')();
co(function*() {
server = app.listen(3000);
yield new Promise((res, rej) => {
server.on('listening', res);
server.on('error', rej);
});
console.log('Listening on port 3000.');
}).catch(function(err) {
console.log(err.stack);
});
app.listen(3000)
不会回复承诺
而不是:
server = yield app.listen(3000);
您可以执行以下操作:
server = app.listen(3000);
yield new Promise(res => server.on('listening', res));
或者更好:
server = app.listen(3000);
yield new Promise((res, rej) => {
server.on('listening', res);
server.on('error', rej);
});
使用此示例进行测试:
var co = require('co');
var app = require('express')();
co(function*() {
server = app.listen(3000);
yield new Promise((res, rej) => {
server.on('listening', res);
server.on('error', rej);
});
console.log('Listening on port 3000.');
}).catch(function(err) {
console.log(err.stack);
});