JavaScript - Client Object Model - Basics

//Get current context
var ctx = new SP.ClientContext.get_current();

//Get other site (web) context
var ctx = new SP.ClientContext("/othersite/");

//Get web
var web = ctx.get_web();

//Get current page ID in Pages library
var pageID = SP.PageContextInfo.get_pageItemId();

//Get current user
var user = ctx.get_web().get_currentUser();
user.retrieve();
var userlogin = user.get_loginName();

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