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

window.myVar or window["myVar"] is an explicit way to refer to a global variable.

A variable is a global variable if it's declared outside of a function (with or without "var"), or if it's declared inside a function without using "var", or if it's declared as window.myVar or window["myVar"].

A variable is declared by either assigning a value to it, or by using the keyword var.

One case where it's useful to refer to a global variable as window.myVar is if you're inside a function that has a local variable called myvar. In that case, myVar refers to the local variable, while window.myVar refers to the global variable.