How can I check if a variable exist in JavaScript?

Question

I am not asking if the variable is undefined or if it is null. I want to check if the variable exists or not. Is this possible?

Answer 1

try this

var ex=false;
try {(ex=myvar)||(ex=true)}catch(e) {}
alert(ex);

where ex is true if myvar has been declared.

working example: http://jsfiddle.net/wcqLz/