typescript string null or empty code example

Example 1: how to check is null or empty in typescript

if(typeof propertyValue!='undefined' && propertyValue){
	//execute code here
}

Example 2: typescript if string is null or empty

function empty(e) {
  switch (e) {
    case "":
    case 0:
    case "0":
    case null:
    case false:
    case typeof(e) == "undefined":
      return true;
    default:
      return false;
  }
}

empty(null) // true
empty(0) // true
empty(7) // false
empty("") // true
empty((function() {
    return ""
})) // false