Find JSON value based on Max date in another field

Question

I have a JSON response body that looks like this:

[
    {
        "ExperimentPlanningId": 20,
        "ExperimentId": "PT1011",
        "AnalystId": 2,
        "ExperimentTemplateId": 1,
        "NumberoFPools": null,
        "ExperimentStatus": "InProgress",
        "NextProcess": "234343",
        "CurrentProcess": "Test Process 1",
        "NextStage": "Stage 1 2",
        "CurrentStage": "Stage 1 2",
        "NextProcessStartDate": "2022-10-15T14:00:00+00:00",
        "CurrentProcessEndDate": "2022-10-15T14:00:00+00:00",
        "ExperimentStartDate": "2022-10-14T15:00:00+00:00",
        "ProjectedOutcome": null,
        "ExperimentalDesign": null,
        "IsActive": true,
        "CreatedDate": "2022-10-14T20:10:42.8276862+00:00"
        
    },
    {
        "ExperimentPlanningId": 20,
        "ExperimentId": "JD2994",
        "AnalystId": 2,
        "ExperimentTemplateId": 1,
        "NumberoFPools": null,
        "ExperimentStatus": "InProgress",
        "NextProcess": "234343",
        "CurrentProcess": "Test Process 1",
        "NextStage": "Stage 1 2",
        "CurrentStage": "Stage 1 2",
        "NextProcessStartDate": "2022-10-15T14:00:00+00:00",
        "CurrentProcessEndDate": "2022-10-15T14:00:00+00:00",
        "ExperimentStartDate": "2022-10-14T15:00:00+00:00",
        "ProjectedOutcome": null,
        "ExperimentalDesign": null,
        "IsActive": true,
        "CreatedDate": "2023-03-31T16:23:19.5981913+00:00"
    }
]

I want to loop through the response body in Postman, find the MAX CreatedDate and store the ExperimentId associated with it, in a variable. So in the example above I'd want to store JD2994 in a variable.

I started with this, but am getting a max is not defined error:

var jsonData = JSON.parse(responseBody)

for (var i=0, len = jsonData.length; i<len; i++) {
  var value = max(jsonData[i]["CreatedDate"]);
}

Answer 1

Here is a better loop

let maxDate = 0;
let maxId = "";
data.forEach(({CreatedDate, ExperimentId}) => {
  const d = new Date(CreatedDate).getTime();
  if (d > maxDate) {
    maxId = ExperimentId;
    maxDate = d;
  }
})
console.log(new Date(maxDate), maxId)

<script>
data = [
    {
        "ExperimentPlanningId": 20,
        "ExperimentId": "PT1011",
        "AnalystId": 2,
        "ExperimentTemplateId": 1,
        "NumberoFPools": null,
        "ExperimentStatus": "InProgress",
        "NextProcess": "234343",
        "CurrentProcess": "Test Process 1",
        "NextStage": "Stage 1 2",
        "CurrentStage": "Stage 1 2",
        "NextProcessStartDate": "2022-10-15T14:00:00+00:00",
        "CurrentProcessEndDate": "2022-10-15T14:00:00+00:00",
        "ExperimentStartDate": "2022-10-14T15:00:00+00:00",
        "ProjectedOutcome": null,
        "ExperimentalDesign": null,
        "IsActive": true,
        "CreatedDate": "2022-10-14T20:10:42.8276862+00:00"
        
    },
    {
        "ExperimentPlanningId": 20,
        "ExperimentId": "JD2994",
        "AnalystId": 2,
        "ExperimentTemplateId": 1,
        "NumberoFPools": null,
        "ExperimentStatus": "InProgress",
        "NextProcess": "234343",
        "CurrentProcess": "Test Process 1",
        "NextStage": "Stage 1 2",
        "CurrentStage": "Stage 1 2",
        "NextProcessStartDate": "2022-10-15T14:00:00+00:00",
        "CurrentProcessEndDate": "2022-10-15T14:00:00+00:00",
        "ExperimentStartDate": "2022-10-14T15:00:00+00:00",
        "ProjectedOutcome": null,
        "ExperimentalDesign": null,
        "IsActive": true,
        "CreatedDate": "2023-03-31T16:23:19.5981913+00:00"
    }
]</script>

Reduce:

const maxId = data.reduce((savedMax, {CreatedDate, ExperimentId}) => {
  if (CreatedDate > savedMax.date) { // the date format is string comparable
    savedMax.date = CreatedDate;
    savedMax.id = ExperimentId;
  }
  return savedMax;
}, { date: "", id: ""}); // initialise savedMax
console.log(maxId);

<script>
  data = [{
      "ExperimentPlanningId": 20,
      "ExperimentId": "PT1011",
      "AnalystId": 2,
      "ExperimentTemplateId": 1,
      "NumberoFPools": null,
      "ExperimentStatus": "InProgress",
      "NextProcess": "234343",
      "CurrentProcess": "Test Process 1",
      "NextStage": "Stage 1 2",
      "CurrentStage": "Stage 1 2",
      "NextProcessStartDate": "2022-10-15T14:00:00+00:00",
      "CurrentProcessEndDate": "2022-10-15T14:00:00+00:00",
      "ExperimentStartDate": "2022-10-14T15:00:00+00:00",
      "ProjectedOutcome": null,
      "ExperimentalDesign": null,
      "IsActive": true,
      "CreatedDate": "2022-10-14T20:10:42.8276862+00:00"

    },
    {
      "ExperimentPlanningId": 20,
      "ExperimentId": "JD2994",
      "AnalystId": 2,
      "ExperimentTemplateId": 1,
      "NumberoFPools": null,
      "ExperimentStatus": "InProgress",
      "NextProcess": "234343",
      "CurrentProcess": "Test Process 1",
      "NextStage": "Stage 1 2",
      "CurrentStage": "Stage 1 2",
      "NextProcessStartDate": "2022-10-15T14:00:00+00:00",
      "CurrentProcessEndDate": "2022-10-15T14:00:00+00:00",
      "ExperimentStartDate": "2022-10-14T15:00:00+00:00",
      "ProjectedOutcome": null,
      "ExperimentalDesign": null,
      "IsActive": true,
      "CreatedDate": "2023-03-31T16:23:19.5981913+00:00"
    }
  ]
</script>