JSFiddle - React, Tailwind, and code Playground

JavaScript

var data = {},my_array,out
  data.d1 = 1
  data.d2 = 2
  data.d3 = undefined
  data.d4 = 4
  data.d5 = 5
  data.d6 = 6
  my_array = [data.d1,data.d2,data.d3]
  out = true;
for(var elem in my_array){
    if (my_array[elem] == undefined){    
       out=false
    }
}

alert(out)