Detecting and fixing circular references in JavaScript

Question

Given I have a circular reference in a large JavaScript object

And I try JSON.stringify(problematicObject)

And the browser throws

Answer 1

Here is a Node ES6 version mixed from the answers from @Aaron V and @user4976005, it fixes the problem with the call to hasOwnProperty:

const isCyclic = (obj => {
  const keys = []
  const stack = []
  const stackSet = new Set()
  let detected = false

  const detect = ((object, key) => {
    if (!(object instanceof Object))
      return

    if (stackSet.has(object)) { // it's cyclic! Print the object and its locations.
      const oldindex = stack.indexOf(object)
      const l1 = `${keys.join('.')}.${key}`
      const l2 = keys.slice(0, oldindex + 1).join('.')
      console.log(`CIRCULAR: ${l1} = ${l2} = ${object}`)
      console.log(object)
      detected = true
      return
    }

    keys.push(key)
    stack.push(object)
    stackSet.add(object)
    Object.keys(object).forEach(k => { // dive on the object's children
      if (k && Object.prototype.hasOwnProperty.call(object, k))
        detect(object[k], k)
    })

    keys.pop()
    stack.pop()
    stackSet.delete(object)
  })

  detect(obj, 'obj')
  return detected
})