Check for unsaved changes before navigation (#156)

[JSn1nj4]

Starting use cases

• [ ] Confirmation for model-based forms with changes
• [ ] Confirmation for generic forms that have fields

Implementation

• [ ] Build dirty states register
  • [x] set method: hash (string), isDirty (boolean)
  • [ ] Key for model: hashed model type + ID?
  • [ ] Key for other forms: hashed form ID + fields IDs?
  • [x] unset method: hash
  • [x] Public computed isClean property that reports overall dirtiness or cleanliness of state
• [ ] Navigation watcher
  • [x] Watches for beforeunload and any other selected events
  • [x] Checks if register isClean
  • [x] Confirms if navigation should happen
• [ ] Reporter implementation
  • [ ] 3 methods matching 3 basic events checked by register
  • [ ] a custom receive event defined by the reporter
  • [ ] a receive method for listening for the above event and acting accordingly

Sample reporter implementation

function reportDirty(hashVal, isDirty) {
  dispatchEvent(new CustomEvent('reportDirtyState', {detail: {hashVal, isDirty}})
}

function checkDirty(hashVal, emitBack) {
  dispatchEvent(new CustomEvent('checkDirtyState', {detail: {hashVal, emitBack}})
}

function receiver({detail: {isDirty}}) {
  console.info(`isDirty: ${isDirty}`)
  // some kind of usage here
}

function forgetDirty(hashVal) {
  dispatchEvent(new CustomEvent('forgetDirtyState', {detail: {hashVal}}))
}

let receiveEvent = 'reporter:receive'
window.addEventListener(receiveEvent, receiver)

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Fixes #156

[JSn1nj4]

Not happening