CODE EXAMPLE FOR JAVASCRIPT

javascript check if undefined

const obj =
{
  "name": "John Doe",
  "age": 39,
  "Street": "Hauptstraße 5"
}
// street is undefined (its uppercase)
var { name: fullname, age, street } = obj;

// You need an array [...]
// if you will check one variable
TestUndef([age]);
// or more
TestUndef([fullname, street, age]);

console.log("All Ok");

function TestUndef(what) {
  for (var that of what) {
    if (typeof (that) == "undefined") {
      throw new Error(`UNDEFINDED OBJECTS!`);
    }
  }
}
// no write "street" in line 5 lowercase, then its all ok.