Facebook Page Invite all at once

To invite to events:

elms=document.getElementsByName("checkableitems[]");
for (i=0;i<elms.length;i++){if (elms[i].type="checkbox" )elms[i].click()}

To invite to pages:

var inputs = document.getElementsByClassName('uiButton _1sm'); 
for(var i=0; i<inputs.length;i++) { inputs[i].click(); } 

Be aware that Facebook now disables the console to prevent an ongoing scam, you can enable it here: https://www.facebook.com/selfxss
But please, when you do, only execute javascript in the console that you can really trust!