A simple errors-safe function allowing to access properties of objects/arrays by string key like

getProperty.js

const getProperty = (obj, path, defaultValue) => {
  const tokens = path.split(/[.[\]]+/g).filter(Boolean)

  if (!obj || typeof obj !== "object") return defaultValue

  if (tokens.length === 1) {
    return (obj[tokens[0]] === undefined) ? defaultValue : obj[tokens[0]]
  }

  return getProperty(obj[tokens[0]], tokens.slice(1).join("."), defaultValue)
}

// example
const obj = { a: 3, b: [1, 2, 3], c: { d: 42 } }

console.log(getProperty(obj, "c.d")) // 42
console.log(getProperty(obj, "c.d.e")) // undefined
console.log(getProperty(obj, "c.d.e", "ooops")) // ooops
console.log(getProperty(obj, "b[0]")) // 1
console.log(getProperty(obj, "b.2")) // 2