How do I check if an object is within an array in Javascript?

Question

I am getting stuck on a project where I am trying to pull out relevant data from a super massive Google Maps Timeline json, and running into the problem of the structure not being as orderly as I thought it was. Essentially, I am trying to pull out an address, time, date and mileage out of this json for every trip in my car. to use this data, I pasted it into a normal javascript file and named it so I can use it as an object. I then take this data and create a string that will format that info like a CSV file.

From going over the structure of the json by looking at only a few trips, I was able to determine the following general structure:

const google = {
   timelineObjects: [
      0: {activitySegment: {A NUMBER OF OBJECTS}},
      1: {placeVisit : {A NUMBER OF OBJECTS}},
      2: {activitySegment: {A NUMBER OF OBJECTS}},
      3: {placeVisit : {A NUMBER OF OBJECTS}}
   ]
}

activitySegment has all the travelling info, like distance, travel times, etc. placeVisit has info about the destination. In my small sample, I was able to just loop through each using an if statement with i%2=0, and just change what I wanted to pull out from each, which worked well.

When I tried adding a larger sample, I was finding that Google occasionally did not create a activitySegment object and only had a placeVisit, which was throwing "Uncaught TypeError: Cannot read property 'distance' of undefined".

I am sure that the even/odd sorting will not work out any more. Is there a way to use a conditional to show if google[timelineObjects][i] is either a {activitySegment} or {placeVisit}? Or, is there a better way to figuring out what object is next in the array?

Answer 1

You can test to see if the Object at the particular array index has a given property using Object.prototype.hasOwnProperty():

const google = {
   timelineObjects: [
      {activitySegment: {}},
      {placeVisit : {}},
      {activitySegment: {}},
      {placeVisit : {}}
   ]
};

console.log(google.timelineObjects[0].hasOwnProperty("activitySegment")); // true
console.log(google.timelineObjects[1].hasOwnProperty("activitySegment")); // false