Wait for Variable to be Defined

//Interval will run/tick every second until  'variable' is set to something (defined)

var interval = setInterval(function() {

console.log('Interval Running');

if( variable == "undefined" || variable == ""){

//Do Something While Waiting / Spinner Gif etc.

}else{

console.log('Interval Stopped');

clearInterval(interval);

}

}, 1000);