Is there a way to trigger scroll event with HtmlUnit or is it not possible at all?

i would suggest u use casperjs instead of htmlunit in this situation, i tried use htmlunit to open pinterest and got

runtimeError: message=[Property 0 not found.] sourceName=[https://s.pinimg.com/webapp/js/vendor-react-d20f99c48b5d58e4821c.js] line=[1] lineSource=[null] lineOffset=[0]

so it does look htmlunit don't have a good support for js, even the latest version 2.31..

here is a demo code using casperjs:

var utils = require('utils')var fs = require('fs')var system = require('system')var casper = require('casper').create({    verbose: true,    logLevel: 'debug',    localToRemoteUrlAccessEnabled: true,    webSecurityEnabled: false,    plainTextAllContent: false,    viewportSize: {        width: 1440,        height: 800    },    onError: function(casper, msg, backtrace) {        utils.dump(backtrace)    }});var cookie = fs.read('cookie.txt').trim() casper.on('started', function() {    this.page.onError = function(msg, trace) {        casper.echo('Error => ' + msg + '\nError trace => ')        utils.dump(trace)    }    this.page.customHeaders = {        "User-Agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.139 Safari/537.36",        "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",        "Accept-Language": "zh-CN,en;q=0.5",        "Accept-Encoding": "gzip, deflate",        "Connection": "keep-alive",        "Pragma": "no-cache",        "Cookie": cookie    }});casper.start('https://www.pinterest.com', function() {    this.then(function() {        this.waitForSelector('div[class="_wx _2h"]', function() {            this.echo("waitForSelector 'div[class=_wx _2h]' is done")            this.scrollTo(0, 1000);            this.wait(5000, function() {                this.scrollTo(0, 2000);            })        })    })});

save above code to a file say named demo.js, then use following command to start casperjs

casperjs --engine=slimerjs demo.js

then u will see the firefox browser startup visually and working!