const data = '{"name":"Sarah","age":25,"skills":["JavaScript","Python"]}'
const parsed = JSON.parse(data)
const stringified = JSON.stringify(parsed, null, 0)
const reparsed = JSON.parse(stringified)

try {
  const invalid = '{name:"John","incomplete":}'
  JSON.parse(invalid)
} catch (e) {
  console.log(e.name)
}

console.log(typeof parsed.age)
console.log(reparsed.skills.length)
console.log(JSON.stringify({a: undefined, b: null, c: 0}))