phantomjs page.evaluate not logging onto console

问题:

I am a PhantomJs newbie. Just checked a similar post on this site. My question is why 'foo' is not logged to console or printed?

var page = require('webpage').create() var foo = 42;  function evaluate(page, func) {     var args = [].slice.call(arguments, 2);     var fn = "function() { return (" + func.toString() + ").apply(this, " + JSON.stringify(args) + ");}";     return page.evaluate(fn); }  page.open('http://google.com', function() {   var foo = 42;   evaluate(page, function(foo) {   console.log(foo);         },foo);  }); 

回答1:

The call page.evaluate() runs your evaluated code in a sandbox. The sandbox's console is not the same as PhantomJS's console.

The following lines added to your script will print your page's console to stderr.

var system = require('system');  page.onConsoleMessage = function(msg) {     system.stderr.writeLine('console: ' + msg); }; 

A more complete implementation would be:

var page = require('webpage').create() var system = require('system'); var foo = 42;  page.onConsoleMessage = function(msg) {   system.stderr.writeLine( 'console: ' + msg ); };  function evaluate(page, func) {   var args = [].slice.call(arguments, 2);   var fn = "function() { return (" + func.toString() + ").apply(this, " +     JSON.stringify(args) + ");}";   return page.evaluate(fn); }  page.open(   'http://google.com',   function() {     var foo = 42;     evaluate(       page,       function(foo) {         console.log(foo);       },       foo     );      console.log( "Done" );      phantom.exit( 0 ); // must exit somewhere in the script   } ); 

Outputs:

$ phantomjs /tmp/idiot.js  console: 42 Done 

By the way, you can call page.open using "about:blank" as your URL if you just want to sandbox test the evaluate function.

回答2:

Output to standard error did not work for me

a work around is assigning :

window.console.log = function(msg) { alert(msg) };  

inside the page.evaluate

Then use :

page.onAlert = function(msg) {   console.log(msg); }; 

to catch the alert

回答3:

There were some problems in the past with console logging, but with the current version on phantomjs (1.9.8), you can do:

page.onConsoleMessage = function (msg) {   console.log(msg); }; 

then fire away your console.logs in the evaluate's callback:

page.evaluate(function() {   console.log("some logged message"); }); 

回答4:

I'm using phantomjs to automate some Google Closure tests and ran into an issue I needed to debug. I was able to dispatch custom events from my test page and receive them inside page.evaluate.

File to log messages:

function logger(msg) {   var evt = document.createEvent('CustomEvent');  // MUST be 'CustomEvent'   evt.initCustomEvent('logger', false, false, msg);   document.dispatchEvent(evt); }  logger('my debug message'); 

Phantomjs file. Here I'm using a saveMessage method to store the string, but you can make that something more appropriate to your needs.

var exec = page.evaluate(function () {   window.phantomRunner = new window.goog.testing.TestRunner();   window.phantomTest = new window.goog.testing.TestCase();    // Listen for `logger` events. The message is stored inside the event's detail property.   document.addEventListener('logger', function(e) {     window.phantomTest.saveMessage(e.detail);   });    window.phantomTest.autoDiscoverTests();   window.phantomRunner.initialize(window.phantomTest);   window.phantomRunner.execute();   return (window.phantomTest.result_.messages); }) 

回答5:

Make sure your phantomjs setting does not disable executing javascript

page.settings.javascriptEnabled = true; 

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