var steps=[];
var testindex = 0;
var loadInProgress = false;
var webPage = require('webpage');
var page = webPage.create();
page.settings.userAgent = 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/44.0.2403.157 Safari/537.36';
page.settings.javascriptEnabled = true;
page.settings.loadImages = false;//Script is much faster with this field set to false
phantom.cookiesEnabled = true;
phantom.javascriptEnabled = true;

//HERE I DEFINE VARIABLES!!!!!!!!!!!!!!!!!!!!!!
var username = "MyUserName";
var password = "MyPassWord";

steps = [
    //Step 1 - Open Facebook home page
    function(){
        page.open("https://www.facebook.com/", function(status){
        });
    },
    function(){
    page.evaluate(function(){
      //HERE OCCURS THE PROBLEM ReferenceError: Can't find variable username undefined:3 :6
      console.log(username);
      document.getElementById("email").value = username;
      document.getElementById("pass").value = password;
      document.getElementById("loginbutton").click();
        });
    }
];

//Execute steps one by one
interval = setInterval(executeRequestsStepByStep,100);


function executeRequestsStepByStep(){
    if (loadInProgress == false && typeof steps[testindex] == "function") {
        steps[testindex]();
        testindex++;
    }
    if (typeof steps[testindex] != "function") {
      //  console.log(page.content)
        console.log("finished");
        page.render('face.png');
        phantom.exit();
    }
}


page.onLoadStarted = function() {
    loadInProgress = true;
};
page.onLoadFinished = function() {
    loadInProgress = false;
};
page.onConsoleMessage = function(msg) {
    console.log(msg);
};