In JavaScript how to check if a variable is null/undefined?

Question

I have a variable created by some rails in my controller that looks like this:

@myvar= row["myvar"]

and I want to pass it into some javascript that is referenced from within my view:

view:

js (play_time):

I am trying to pass " into the js [obviously that is not the right syntax]. Can anyone help?

Answer 1

In Javascript you can check by using typeof for undefined variables

Example:

if(typeof(variable) == 'undefined')
    {
        alert("Variable is undefined");
    }
if(variable == null) 
   {
       alert("Variable is null");
   }