create array of objects from an array of string ids with 1st object having first value with second, second with third and so on

Question

I have an array of strings e.g. const array1 = ["124542", "112244", "112245", "112246"];

I want to create below results:

const array2 = [
  {
    "comparableId": "124542",
    "comparatorId": "112244"
  },
  {
    "comparableId": "112244",
    "comparatorId": "112245"
  },
  {
    "comparableId": "112245",
    "comparatorId": "112246"
  }
]

In this array2, 1st index value from array1 is with 2nd value, 2nd value with 3rd and 3rd with 4th and so on. This array1 is dynamic and can have just 1 value e.g. const array1 = ["124542"]; and can have any number of values.

I have tried using Ecma Script reduce and map methods.

const array2 = array1.map((value, index) => {
    return {
       comparableId: value,
       comparatorId: array1[index + 1] || '',
    };
});

Is there some other good way to do it ?

lusc · Accepted Answer · 2022-06-06 09:29:33Z

4

Using a for loop is probably the easiest here.

const array1 = ["124542", "112244", "112245", "112246"];


const transform = (array) => {
  const result = [];

  for (let i = 0; i === 0 || i < array.length - 1; ++i) {
    result.push({
      comparableId: array[i],
      comparatorId: array[i + 1] ?? "",
    })
  }
  
  return result;
};

console.log(transform(array1));
console.log(transform(["124542"]));

edited Jun 6, 2022 at 9:29

answered Jun 6, 2022 at 9:21

lusc

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1 Comment

Owais Over a year ago

try this for a single value in the array1 e.g. const array1=["124542"]; It will give an empty array result. For that, we need to have array2 = [ { "comparableId": "124542", "comparatorId": "" } ]

Asplund · Accepted Answer · 2022-06-06 09:23:57Z

0

Fully declarative, no mutations solution.

const
  array1 = ["124542", "112244", "112245", "112246"],
  array2 = [...Array(Math.ceil(array1.length / 2))].map((_, i) =>
    ({comparableId: array1[i * 2], comparatorId: array1[i * 2 + 1] ?? ""})
  );

console.log(array2);

answered Jun 6, 2022 at 9:23

Asplund

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2 Comments

Owais Over a year ago

some results are skipped, now.

Asplund Over a year ago

What results?..

Hans Murangaza DRCongo · Accepted Answer · 2022-06-06 09:42:17Z

0

const array1 = ["124542", "112244", "112245", "112246"];

let array2 = [];

array1.map((item, index) =>{
  
  array2.push({comparableId: item, comparatorId: array1[index+1] || ""})
})
console.log(array2)

edited Jun 6, 2022 at 9:42

answered Jun 6, 2022 at 9:21

Hans Murangaza DRCongo

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2 Comments

Owais Over a year ago

try this for a single value in the array1 e.g. const array1=["124542"]; It will give an empty array result. For that, we need to have array2 = [ { "comparableId": "124542", "comparatorId": "" } ]

Hans Murangaza DRCongo Over a year ago

already improved

stickynotememo · Accepted Answer · 2022-06-06 09:54:45Z

0

A loop is the best option.

const array1 = ["124542", "112244", "112245", "112246"]
let array2 = [];
for (let i = 0; i < array1.length; i + 2) {
  array2[i] = {
    "comparableId": array2[i],
    "comparatorId": array2[i + 1]
  }
  console.log(array2[i])
}

array2 won't be a const variable as it is going to be modified each loop. If you really need it to be a constant then you'll have to define a new constant like so: const array3 = array2; at the end of your code.

answered Jun 6, 2022 at 9:54

stickynotememo

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2 Comments

TAHER El Mehdi Over a year ago

"array2 won't be a const variable"? Yes it should be const, and each loop array2.push({...})

stickynotememo Over a year ago

@TAHERElMehdi Wouldn't array2.push() result in an error because the value is a const? it has to be variable so that it can be modified by .push

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