main.js

let input = "{\"id\": 1, \"cell\":{\"id\":\"12345678-etc\"}}";
let obj = JSON.parse(input)

console.log(obj.cell.id); // 12345678-etc

let match = obj.cell.id.match(/^\d*/);
let id = match[0];

console.log(id) // 12345678
console.log(typeof id) // string

id = parseFloat(id);

console.log(id) // 12345678
console.log(typeof id) // number