节点7.10 -等待支持吗？

Question

我在节点7.10上：

$ node --version
v7.10.0

我认为它支持await。

 let result = await Weather.findOne(options, function(err, weather) {

    if (err) {
        res.set('Content-Type', 'application/json');
        return res.status(200).send('Error occurs: ' + err);
    }

    if (weather) {
        res.set('Content-Type', 'application/json');
        return res.status(200).send(key + ' already exist.');
    }

    return weather;
});

console.log(result);

错误消息：

let result = await Weather.findOne(options, function(err, weather) {
                       ^^^^^^^
SyntaxError: Unexpected identifier
    at createScript (vm.js:53:10)
    at Object.runInThisContext (vm.js:95:10)
    at Module._compile (module.js:543:28)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)
    at Module.require (module.js:498:17)
    at require (internal/module.js:20:19)
    at Object.<anonymous> (/var/www/html/projects/citizen-sense-dustbox-data-streams/es5/v4/app.js:33:15)
    at Module._compile (module.js:571:32)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)
    at Module.require (module.js:498:17)
    at require (internal/module.js:20:19)
    at Object.<anonymous> (/var/www/html/projects/citizen-sense-dustbox-data-streams/es5/v4/bin/www:7:11)
    at Module._compile (module.js:571:32)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)
    at Module.runMain (module.js:605:10)
    at run (bootstrap_node.js:427:7)
    at startup (bootstrap_node.js:151:9)
    at bootstrap_node.js:542:3

在节点7.10中似乎不支持？还是我做错什么了？

有什么想法吗？

Answer 1

来自https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await

等待操作员用来等待承诺。只能在异步函数中使用。

async function doAwait() {
    let result = await Weather.findOne(options, function(err, weather) {

       if (err) {
            res.set('Content-Type', 'application/json');
           return res.status(200).send('Error occurs: ' + err);
       }

       if (weather) {
           res.set('Content-Type', 'application/json');
           return res.status(200).send(key + ' already exist.');
       }

       return weather;
   });

   console.log(result);
}

Answer 2

我有v7.10.0，并且在那个版本中肯定支持await/异步。我想它是在7.4中添加的，但不确定。

ubuntu@ubuntu:~$ node --version
v7.10.0

当我跑步时：

const getDate = async () => {
    return new Date()
}
const printDate = async () => {
    const date = await getDate()
    return date
}
printDate().then(console.log).catch(console.error)

我得到：

2017-07-04T09:04:27.311Z

编辑:只是fyi，异步/等待并没有真正进入ES7。不过，它很有可能会进入今年的ECMAScript版。https://github.com/tc39/proposals/blob/master/finished-proposals.md