JavaScript check if variable exists (is defined/initialized)

Question

Which method of checking if a variable has been initialized is better/correct? (Assuming the variable could hold anything (string, int, object, function, etc.))

Answer 1

you can use the typeof operator.

For example,

var dataSet;

alert("Variable dataSet is : " + typeof dataSet);

Above code snippet will return the output like

variable dataSet is : undefined.