JSFiddle - React, Tailwind, and code Playground

JavaScript

var x ={
        "12" : [ 3, 4 ],
        "13" : [ 3 ],
        "14" : [ 1, 4 ]
        }
  var outputArray = [];
	for(var y in x){
		for(var z = 0; z < x[y].length; z++){
			if(outputArray.indexOf(x[y][z]) === -1){
				outputArray.push(x[y][z]);
			}
		}
	}
  
  console.log(outputArray);