The following offset values within the array

Question

The following offset values within the array

Currently, I am trying to extract an array of elements using the following code:

const result = payload.map(({QUALITY, TEMPERATURE, SENSOR_READING_DATETIME, SOURCE_COMPONENT_ID, SENSOR_NAME, NEXT_OFFSET})=> ({
        TELEMATICS: {
          QUALITY,
          TEMPERATURE
        },
      SOURCE_COMPONENT_ID,
      SENSOR_NAME,
      SENSOR_READING_DATETIME,
      NEXT_OFFSET
    }));

The resulting output looks like this:

{
    data: [
            {
                "TELEMATICS": {
                    "QUALITY": 91.98,
                    "TEMPERATURE": 20.5
                },
                "id": 118,
                "SENSOR_READING_DATETIME": "2021-09-24T04:53:06.801Z",
                "SOURCE_COMPONENT_ID": 1,
                "SENSOR_NAME": "TD2",
                "NEXT_OFFSET": 119
            }
            ,
            {
                "TELEMATICS": {
                    "QUALITY": 91.98,
                    "TEMPERATURE": 20.5
                },
                "id": 119,
                "SENSOR_READING_DATETIME": "2021-09-24T05:53:09.774Z",
                "SOURCE_COMPONENT_ID": 1,
                "SENSOR_NAME": "TD2",
                "NEXT_OFFSET": 120
            }
           ]
    }

However, my goal is to extract the NEXT_OFFSET value outside the elements and have it only for the last record in the array.

I would like the output to resemble the example below:

{
    data: [
            {
                "TELEMATICS": {
                    "QUALITY": 91.98,
                    "TEMPERATURE": 20.5
                },
                "id": 118,
                "SENSOR_READING_DATETIME": "2021-09-24T04:53:06.801Z",
                "SOURCE_COMPONENT_ID": 1,
                "SENSOR_NAME": "TD2"
            }
            ,
            {
                "TELEMATICS": {
                    "QUALITY": 91.98,
                    "TEMPERATURE": 20.5
                },
                "id": 119,
                "SENSOR_READING_DATETIME": "2021-09-24T05:53:09.774Z",
                "SOURCE_COMPONENT_ID": 1,
                "SENSOR_NAME": "TD2"
            }
           ],
        "NEXT_OFFSET": 120
}

Could anyone guide me on how to achieve this desired outcome?

javascript arrays json pagination

Answer 1

Answer №1

If you want to accumulate results and add an extra field when reaching the last item, consider using Array.reduce. Setting the initial value of the extra property as null can handle the 'no results' case as well.

A more straightforward approach would be:

const payload = [
  { a: 1, b: 2 },
  { a: 5, b: 6 },
  { a: 10, b: 11 }
];

const res = payload.reduce(
  (acc, { a, b }, index) =>
    index === payload.length - 1
      ? { ...acc, data: [...acc.data, a],b }
      : { ...acc, data: [...acc.data, a] },

  { data: [], b:null }
);

console.log(res);

In a scenario where you fetch batches of items in certain counts, such as REQUEST_COUNT (e.g., 2000), you could implement it like this:

const res = payload.reduce(
  (acc, { NEXT_OFFSET, ...item }, index) => {
    const data = [...acc.data, item];
    if (index < payload.length - 1) {
      return { data };
    } else {
      const nextOffset =
        payload.length < REQUEST_COUNT
          ? { NEXT_OFFSET: null }
          : { NEXT_OFFSET 
       return {data, ...nextOffset}
    }
  },
  { data: [], NEXT_OFFSET: null }
);

Answer 2

If you want to accumulate results and add an extra field when reaching the last item, consider using Array.reduce. Setting the initial value of the extra property as null can handle the 'no results' case as well.

A more straightforward approach would be:

const payload = [
  { a: 1, b: 2 },
  { a: 5, b: 6 },
  { a: 10, b: 11 }
];

const res = payload.reduce(
  (acc, { a, b }, index) =>
    index === payload.length - 1
      ? { ...acc, data: [...acc.data, a],b }
      : { ...acc, data: [...acc.data, a] },

  { data: [], b:null }
);

console.log(res);

In a scenario where you fetch batches of items in certain counts, such as REQUEST_COUNT (e.g., 2000), you could implement it like this:

const res = payload.reduce(
  (acc, { NEXT_OFFSET, ...item }, index) => {
    const data = [...acc.data, item];
    if (index < payload.length - 1) {
      return { data };
    } else {
      const nextOffset =
        payload.length < REQUEST_COUNT
          ? { NEXT_OFFSET: null }
          : { NEXT_OFFSET 
       return {data, ...nextOffset}
    }
  },
  { data: [], NEXT_OFFSET: null }
);

The following offset values within the array

Answer №1

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