GreaseMonkey Navigation wih Left and Right keys

GreaseMonkey Navigation wih Left and Right keys.js

// ==UserScript==
// @name     Navigation wih Left and Right keys
// @version  1
// @grant    none
// @include  http://www.example.com/*
// ==/UserScript==

// USER CONFIG AREA ******************* //
var selector_1 = 'body > table:nth-child(1) > tbody:nth-child(1) > tr:nth-child(2) > td:nth-child(1) > p:nth-child(3) > a:nth-child(1) > img:nth-child(1)';
var selector_2 = 'body > table:nth-child(1) > tbody:nth-child(1) > tr:nth-child(2) > td:nth-child(1) > p:nth-child(3) > a:nth-child(2) > img:nth-child(1)';

// ************************************ //

function eventFire(el, etype){
  if (el.fireEvent) {
    el.fireEvent('on' + etype);
  } else {
    var evObj = document.createEvent('Events');
    evObj.initEvent(etype, true, false);
    el.dispatchEvent(evObj);
  }
}

/*--- Get or set the codes for the arrow keys.
    Firefox gives us nice constants, Chrome does not.
*/
KeyEvent        = (typeof KeyEvent === "object")  ?  KeyEvent  :  [];
const LEFT_KEY  = KeyEvent.DOM_VK_LEFT   ||  37;
const RIGHT_KEY = KeyEvent.DOM_VK_RIGHT  ||  39;

window.addEventListener ("keydown", keyboardHandler, false);

function keyboardHandler (zEvent) {
    var bBlockDefaultAction = false;

    //--- Assume we want only the plain keys, not the modified versions.
    if (zEvent.altKey  ||  zEvent.ctrlKey  ||  zEvent.shiftKey) {
        //-- Do nothing (most user-friendly option, in most cases).
    }
    else {
        if (zEvent.which == LEFT_KEY) {
            //DO LEFT KEY ACTION HERE.
            bBlockDefaultAction = true;
          	var elm = document.querySelectorAll( selector_1 )
            elm[0].click();
        }
        else if (zEvent.which == RIGHT_KEY) {
            //DO RIGHT KEY ACTION HERE.
            bBlockDefaultAction = true;
            var elm = document.querySelectorAll( selector_2 )
            elm[0].click();
        }
    }

    if (bBlockDefaultAction) {
        zEvent.preventDefault ();
        zEvent.stopPropagation ();
    }
}