[рони]

Обозначение позиции товара a,b,c,d,e.

let objJson = {
  "a" : {
    "name" : "coca-cola",
    "cost" : "10",
    "description" : "описание товара 1",
    "image" : "img/Coca-Cola.jpg",
    "type" : "drink",
    "link" : "46147110",
     "pos" : "1"
  },
  "b" : {
    "name" : "кофе",
    "cost" : "10",
    "description" : "описание товара 2",
    "image" : "img/cofe.jpg",
    "link" : "goods/tb-2.html",
    "type" : "drink",
     "pos" : "46147111"
  },
  "c" : {
    "name" : "чипсы",
    "cost" : "30",
    "description" : "описание товара 3",
    "image" : "img/chips.jpeg",
    "link" : "46147112",
    "type" : "snack",
     "pos" : "3"
  },
     "d" : {
    "name" : "сендвич",
    "cost" : "40",
    "description" : "описание товара 4",
    "image" : "img/sandvich.png",
    "link" : "46147113",
    "type" : "pie",
     "pos" : "4"
  },
  "e" : {
    "name" : "coca-cola",
    "cost" : "10",
    "description" : "описание товара 1",
    "image" : "img/Coca-Cola.jpg",
    "type" : "drink",
    "link" : "46147114",
     "pos" : "5"
  }
};
let barcode = "46147110";

function findId(barcode)
{
   for(let [id, obj] of Object.entries(objJson)){
       if(obj.link == barcode) return id
   }
}
let id = findId(barcode);
alert(id);