表达router.get（）函数SyntaxError

Question

I'm trying to create a route to return JSON data from a JSON-RPC API.

My code:

router.get('/balance', function(req, res, client) {
    res.json({
        client.getBalance('*', 1, function(err, balance) {
            if(err)
                console.log(err);
            else
                console.log('Balance: ', balance);
        });
    });
});

It's using the npm package node-litecoin. I have required it and created a client var like so:

var client = new litecoin.Client({
    host: 'localhost',
    port: 9332,
    user: 'myaccount',
    password: 'mypass'
});

client.getBalance('*', 1, function(err, balance) { ^ SyntaxError: Unexpected token .

Why am I getting this error?

Answer 1

Why am I getting this error?

Because client.getBalance('*', 1, function(err, balance) { cannot be there where you put it.

Lets have a closer look:

res.json({ ... });

The {...} here indicate an object literal . The "content" of the literal has to be a comma separated list of key: value pairs, eg

res.json({foo: 'bar'});

You instead put a function call there:

res.json({ client.getBalance(...) });

which simply is invalid.

---

How can I have the route '/balance' output the client.getBalance() function?

It looks like client.getBalance is an asynchronous function call, hence passing its return value to res.json wouldn't work either. You have to pass the result that you get in the callback to res.json :

router.get('/balance', function(req, res) {
    client.getBalance('*', 1, function(err, balance) {
        if(err)
            console.log(err);
        else
            console.log('Balance: ', balance);

        res.json(balance);
    });
});

If you are not very familiar with JavaScript's syntax, I recommend to read the MDN JavaScript Guide .