CODEWITHSUNDEEP
javascriptnode.jsphantomjs
sooon
sooon

Reputation: 4888

Phantom.js - How to use promises instead of callbacks?

I am testing phantom-node with this code:

var http = require('http');
http.createServer(function (req, res) {
  res.write('<html><head></head><body>');
  res.write('<p>Write your HTML content here</p>');
  res.end('</body></html>');
}).listen(1337);

var phantomProxy = require('phantom-proxy');

phantomProxy.create({'debug': true}, function (proxy) {
    proxy.page.open('http://localhost:1337', function (result) {
        proxy.page.render('scratch.png', function (result) {
                proxy.end(function () {
                    console.log('done');
                });
        }, 1000);
    });
});

It works, but I want to change it to something like:

phantomProxy.create()
   .then(something)=>{...}
   .then(something)=>{...}
   .then(something)=>{...}
   .catch((err)=>{
        console.log(err);
        proxy.end();
    }

So that it is easier to read. Any suggestion?

Upvotes: 3

Views: 1556

Answers (1)

dvlsg
dvlsg

Reputation: 5538

Hm. The libraries that handle promisifying may not work correctly, since phantom-proxy doesn't seem to follow the standard function(err, result) node callback signature. There might be some that handle that sort of magic, but I'd be a bit skeptical. I'm a little bit surprised that phantom-proxy doesn't have an error as the first argument for those callbacks.

Either way, you can always do it yourself.

function phantomProxyCreate(opts) {
    return new Promise(resolve => phantomProxy.create(opts, resolve));
}

function proxyPageOpen(url) {
    return (proxy) => {
        // You may need to resolve `proxy` here instead of `result`.
        // I'm not sure what's in `result`.
        // If that's the case, write out the callback for `proxy.page.open`,
        // and then `resolve(proxy)` instead.
        return new Promise(resolve => proxy.page.open(url, resolve)); 
    };
}

If you follow that style, you can do this (note that I'm returning a "curried" function from proxyPageOpen to use in the promise pipeline):

phantomProxyCreate({ debug: true })
    .then(proxyPageOpen('http://localhost:1337'))
    // ... etc

Upvotes: 1

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