How to debug PhantomJS?

[b1th0ven]

I have script test.js:

var page = require('webpage').create();
var fs = require('fs');
var url = 'http:://google.com';
page.open(url, function(status) {
        console.log('1');
phantom.exit();
});};

When I try to run this script in my console it gets hung and nothing happens: 

b1th0ven@compic:/var/www/test/js$ phantom print.js

How and where I can read about errors in script?

It's an example of my typically problem with PhantomJS. When script have an error I can't read about it anything... anywhere. How to debug PhantomJS?  

[Sean McNamara]

You have two colons in "http:://google.com" but you need only one.

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[Dawid Bartosz Janiga]

Phantomjs (^2.1.1) has insufficient error handling IMHO, but there are ways to deal with it.

Errors in webpage

You can intercept any JavaScript errors thrown by WebPage instance (errors which normally you can see in Console tab in DevTools).

Example snippet with dealing it:

page.onError = function (msg, trace) {
    var msgStack = ['PHANTOM ERROR: ' + msg];
    if (trace && trace.length) {
        msgStack.push('TRACE:');
        trace.forEach(function (t) {
            msgStack.push(' -> ' + (t.file || t.sourceURL) + ': ' + t.line + (t.function ? ' (in function ' + t.function + ')' : ''));
        });
    }
    console.error(msgStack.join('\n'));
    phantom.exit(1);
};

In Terminal

➜  phantomjs test.js

PHANTOM ERROR: Error: ni chuja

TRACE:

 -> http://localhost:8000/error.html: 2 (in function global code)

  phantomjs://code/test.js:13 in onError

Errors in phantomJS code

Unfortunately, phantomjs doesn't throw any syntax error, it just hung up. But there is smart way to check syntax. 

➜  node test.js

And results run on your code:

/Users/djaniga/Documents/dawidjaniga/atelier/test.js:7

});};

    ^

SyntaxError: Unexpected token ;

    at exports.runInThisContext (vm.js:53:16)

    at Module._compile (module.js:511:25)

    at Object.Module._extensions..js (module.js:550:10)

    at Module.load (module.js:456:32)

    at tryModuleLoad (module.js:415:12)

    at Function.Module._load (module.js:407:3)

    at Function.Module.runMain (module.js:575:10)

    at startup (node.js:160:18)

    at node.js:445:3

Hope that will be an answer for your question,

cheers.

[b1th0ven]

Thanks, David. But this event don't help me. Let's take a look on this code.

var page = require('webpage').create();

page.open('http://google.com', function(status) {
    console.log("Status: " + status);
    if(status === "success") {
        var a.c = 1;
        console.log(a);
    }
    phantom.exit(0);
});

page.onError = function(msg, trace) {
  console.log('page onError...');
  phantom.exit(1);
};

phantom.onError = function(msg, trace) {
  console.log('phantom onError...');
  phantom.exit(2);
};

Specially for Sean McNamara - I know that code have an error in this line var a.c = 1;

So, when I run script it gets hung and nothing happens... again... 

суббота, 20 августа 2016 г., 19:07:52 UTC+3 пользователь Dawid Bartosz Janiga написал:

[Dawid Bartosz Janiga]

Ok, first of all, describe your goal. If you would like to know about a syntax error, the best way for now is call the script in Node environment - as I mentioned in the example.