Check If Object Exists In JavaScript
Answer : You can safely use the typeof operator on undefined variables. If it has been assigned any value, including null, typeof will return something other than undefined. typeof always returns a string. Therefore if (typeof maybeObject != "undefined") { alert("GOT THERE"); } There are a lot of half-truths here, so I thought I make some things clearer. Actually you can't accurately tell if a variable exists (unless you want to wrap every second line into a try-catch block). The reason is Javascript has this notorious value of undefined which strikingly doesn't mean that the variable is not defined, or that it doesn't exist undefined !== not defined var a; alert(typeof a); // undefined (declared without a value) alert(typeof b); // undefined (not declared) So both a variable that exists and another one that doesn't can report you the undefined type. As for @Kevin's misconception, null == undefined . It is due to type c...