How to debug a PhantomJS script?

Question

My script has some syntax error but instead of showing the error, PhantomJS doesn't display anything. Why Phantom JS isn't showing parse error if he script has errors?

In the following PhantomJS script (running via windows CMD), phantomJs hangs instead of showing error if there is a parsing error in the script.

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

console.log('starting script');

if (system.args.length === 0) {
    console.log('no args');
} else {
    system.args.forEach(function(arg,index){
        console.log('arg is '+arg+' at '+index);
    });
}

webpage.open('http://localhost:3000/cookie-demo',function(status){
    if (status === 'success'){
        console.log('success in opening page');
        phantom.cookies.forEach(function(cookie,index){
            for ( var key in cookie){

/*if instead of index, I use i as variable (undefined), the script just hangs!*/

console.log('[cookie:'+index+']'+key+'='+'cookie[key]');
        }
    });
    phantom.exit(0);
}
else{
    console.log('could not open the page');
    phantom.exit(1);
}

});

If there is no syntax error in the script, I get following output

C:\Users\Manu\Documents\manu\programs\random>phantomjs --cookies-file=cookie-jar.txt phantomTest.js
starting script
arg is phantomTest.js at 0
success in opening page
[cookie:0]domain=cookie[key]
[cookie:0]expires=cookie[key]
[cookie:0]expiry=cookie[key]
[cookie:0]httponly=cookie[key]
[cookie:0]name=cookie[key]
[cookie:0]path=cookie[key]
[cookie:0]secure=cookie[key]
[cookie:0]value=cookie[key]
[cookie:1]domain=cookie[key]
[cookie:1]expires=cookie[key]
[cookie:1]expiry=cookie[key]
[cookie:1]httponly=cookie[key]
[cookie:1]name=cookie[key]
[cookie:1]path=cookie[key]
[cookie:1]secure=cookie[key]
[cookie:1]value=cookie[key]

But if there is a syntax error, I see nothing on the console and it doesnt exit

C:\Users\Manu\Documents\manu\programs\random>phantomjs --cookies-file=cookie-jar.txt phantomTest.js

Answer 1

PhantomJS version 2.0 and 2.1 will silently fail and hang if there are syntax errors. Use versions 1.9.8 or 2.5 betas. All downloads are here: https://bitbucket.org/ariya/phantomjs/downloads/

Better still migrate to Puppeteer which is a project with very similar API that uses headless Google Chrome underneath.