Mongo DB连接

Question

我不知道为什么我的代码没有编译，我有以下代码。

mongoose.connect(db)
         .then( onFulfilled: () => console.log(`MongoDB connected.`))
         .catch( onRejected: err => console.log(err));

这是我得到的错误

[nodemon] app crashed - waiting for file changes before starting...
[nodemon] restarting due to changes...
[nodemon] starting `node server.js`
/home/sambulo/Documents/linkshortenner/server.js:8
         .then( onFulfilled: () => console.log(`MongoDB connected.`))
                ^^^^^^^^^^^

SyntaxError: missing ) after argument list
    at createScript (vm.js:80:10)
    at Object.runInThisContext (vm.js:139:10)
    at Module._compile (module.js:616:28)
    at Object.Module._extensions..js (module.js:663:10)
    at Module.load (module.js:565:32)
    at tryModuleLoad (module.js:505:12)
    at Function.Module._load (module.js:497:3)
    at Function.Module.runMain (module.js:693:10)
    at startup (bootstrap_node.js:188:16)
    at bootstrap_node.js:609:3

Answer 1

.then( onFulfilled: () => console.log(`MongoDB connected.`))

不能完全确定您要在此处执行的操作，似乎您是在then子句中声明了您实际想要具有功能的对象：

.then( () => console.log(`MongoDB connected.`) )

或：

.then( function onFulfilled () { console.log(`MongoDB connected.`) } )

编辑：同样适用于catch()

Answer 2

只需删除onFulfilled和onRejected

然后确保db包含数据库地址。

您的最终代码应如下所示，

mongoose.connect(db)
         .then(() => console.log(`MongoDB connected.`))
         .catch((err) => console.log(err));

Answer 3

Promise有两种方法then()和catch()，

Promise.then(() => {});

Promise.catch(() => {});

Promise
    .then(() => {})
    .catch(() => {});

在您的代码中，您需要删除:并稍稍更新代码...

mongoose.connect(db)
         .then((onFulfilled) => console.log(`MongoDB connected.`))
         .catch((err) => console.log(err));