How read data from a JSON arry object in Javascript

Question

I am trying to get a value from a JSON array in Javascript :

The JSON array looks like :

[
 {
 "_id": 0,
 "_entityMetadataList": [
 {
 "_metadataValue": "/storage/emulated/0/DCIM/.thumbnails/1524101696032.jpg",
 },
 {
 "_metadataValue": "/storage/emulated/0/DCIM/.thumbnails/1524101694488.jpg",
 }
 ],
 "_timeCreated": "Tue Jan 15 06:10:04 2019\n",
 "_timeUpdated": "Tue Jan 15 06:10:04 2019\n",
 "objectEntity": {
 "_id": 0,
 "_EntitySiteGUID": -1
 }
 }
]

How I go about it :

app.post('/sound', function (req, res) {
 let entitiesArray = req.body['filter'];
 console.log('entitiesArray: ' + JSON.stringify(entitiesArray._entityMetadataList[0]._metadataValue))

(this is in a Node environment, by the way)

I, however keep getting the error :

TypeError: Cannot read property '0' of undefined 

Answer 1

Seems you also need to pass the index for revEntitiesArray.

Try this

console.log('revEntitiesArray: ' + 
JSON.stringify(revEntitiesArray[0]._revEntityMetadataList[0]._metadataValue))

Answer 2

Maybe this code can help

data = [
 {
 "_id": 0,
 "_revEntityMetadataList": [
 {
 "_metadataValue": "/storage/emulated/0/DCIM/.thumbnails/1524101696032.jpg",
 },
 {
 "_metadataValue": "/storage/emulated/0/DCIM/.thumbnails/1524101694488.jpg",
 }
 ],
 "_timeCreated": "Tue Jan 15 06:10:04 2019\n",
 "_timeUpdated": "Tue Jan 15 06:10:04 2019\n",
 "revObjectEntity": {
 "_id": 0,
 "_revEntitySiteGUID": -1
 }
 }
]`
data[0]["_revEntityMetadataList"][0]

Answer 3

Looks like you missed that the outermost reference is an array

revEntitiesArray[0]._revEntityMetadataList[0]._metadataValue

When in doubt, assign each part of your path expression to a local variable and step through with a debugger.