Check if a variable is in the scope or not in Javascript

Question

I need to check if a object "objCR" is present in the current scope or not. I tried using below code.

if(objCR == null)
alert("object is not defined");

Let me know where I am wrong.

Answer 1

Use the typeof operator:

if(typeof objCR == "undefined")
   alert("objCR is not defined");

Answer 2

if (typeof objCR=="undefined"){
    alert("objCR is undefined");
} else {
    alert("objCR is defined");
};

(!objCR) will return true if objCR is a boolean equal to false