window.variableName

Question

I am going through some code and at the beginning of the script we have var emailID = email. Later on, the code refers to emailID by going window.emailID<

Answer 1

It is used to define global variable in JavaScript.

globalVar = "Hello World";
function function1(){
    alert(window.globalVar);
} 
function1();

This will print "Hello World" in the popup.

    function function1(){ 
        globalVar = "Hello World";
        alert(window.globalVar);
    }function function2(){
        alert(window.globalVar);
    } 
    function1(); 
    function2();

This will create two popups with value "Hello World", one from function1() and another from function2().

So, by using window we can call a variable from any scope in javascript.