How to Merge Items within an Array of Objects Using Typescript?

Question

How to Merge Items within an Array of Objects Using Typescript?

I'm currently facing a challenge in combining objects from an array of Objects in typescript.

The structure of the array is as follows:

0: {type: 'FeatureCollection', features: Array(134)}
1: {type: 'FeatureCollection', features: Array(109)}

What I am looking for is to create a single object (not an array) with all "features" combined, like this:

{type: 'FeatureCollection', features: Array(243)}

As I am new to typescript, please excuse me if this seems like a basic question...

Thank you for your help!

EDIT: To clarify, when I mention Array(134), it means there are 134 objects inside. The manual approach for a collection of length 2 is shown below:

const result = [...collection[0].features, ...collection[1].features];
const resultCollection: FeatureCollection = collection[0];
resultCollection.features = result;

I need to generalize this solution to work for any length of collection.

javascript arrays typescript javascript-objects

Answer 1

Answer №1

Need help achieving a similar result? By incorporating types, you can combine the arrays of `features` from all elements within the `data` array using vanilla JavaScript methods.

Initialize an `output` object and define its `type` property.
Utilize Array#filter to filter out entries in `data` based on their type.
Leverage Array#flatMap to extract the `features` arrays from these filtered entries and merge them into one single array.

const data = [
  { type: 'FeatureCollection', features: [1, 2, 3] },
  { type: 'FeatureCollection', features: [4, 5, 6] }
];

const output = { 
  type: 'FeatureCollection',
  features: data
    .filter(obj => obj.type === 'FeatureCollection')
    .flatMap(obj => obj.features) 
};
  
console.dir(output);

Answer 2

Need help achieving a similar result? By incorporating types, you can combine the arrays of `features` from all elements within the `data` array using vanilla JavaScript methods.

Initialize an `output` object and define its `type` property.
Utilize Array#filter to filter out entries in `data` based on their type.
Leverage Array#flatMap to extract the `features` arrays from these filtered entries and merge them into one single array.

const data = [
  { type: 'FeatureCollection', features: [1, 2, 3] },
  { type: 'FeatureCollection', features: [4, 5, 6] }
];

const output = { 
  type: 'FeatureCollection',
  features: data
    .filter(obj => obj.type === 'FeatureCollection')
    .flatMap(obj => obj.features) 
};
  
console.dir(output);

Answer 3

Answer №2

To simplify the process, utilize the Array.prototype.reduce method along with the spread operator

const items = [
  { category: "apple", attributes: ["red", "juicy", "sweet"] },
  { category: "apple", attributes: ["sour", "crisp", "healthy"] },
];

const mergeAttributes = (items) => items.reduce((accumulator, current) => {
  accumulator.attributes = [...(accumulator.attributes ?? []), ...current.attributes];
  return accumulator;
}, { category: (items[0].category) });

console.log(mergeAttributes(items));

Answer 4

To simplify the process, utilize the Array.prototype.reduce method along with the spread operator

const items = [
  { category: "apple", attributes: ["red", "juicy", "sweet"] },
  { category: "apple", attributes: ["sour", "crisp", "healthy"] },
];

const mergeAttributes = (items) => items.reduce((accumulator, current) => {
  accumulator.attributes = [...(accumulator.attributes ?? []), ...current.attributes];
  return accumulator;
}, { category: (items[0].category) });

console.log(mergeAttributes(items));

Answer 5

Answer №3

When using the reduce method :

const array = [
  {type: 'FeatureCollection', features: [1, 2, 3]},
  {type: 'FeatureCollection', features: [4, 5, 6]},
  {type: 'Test', features: [4, 5, 6]}
]

const merged = array.reduce((arr, item) => {
  const found = arr.find((i) => i.type === item.type);
  if (found) {
    found.features.push(...item.features);
  } else {
    arr.push(item);
  }
  return arr;
}, []);

console.log(merged);

---- MODIFIED ----

alternative approach :

const array = [
  {type: 'FeatureCollection', features: [1, 2, 3]},
  {type: 'FeatureCollection', features: [4, 5, 6]},
  {type: 'Test', features: [4, 5, 6]}
]

const merged = array.reduce((obj, item) => {
  if (obj[item.type]) {
    obj[item.type].push(...item.features);
  } else {
    obj[item.type] = item.features;
  }
  return obj;
}, {} as {[key: string]: number[]});

const keys = Object.keys(merged);
const result = keys.map((k) => ({type: k, features: merged[k]}));

console.log(result);

Answer 6

When using the reduce method :

const array = [
  {type: 'FeatureCollection', features: [1, 2, 3]},
  {type: 'FeatureCollection', features: [4, 5, 6]},
  {type: 'Test', features: [4, 5, 6]}
]

const merged = array.reduce((arr, item) => {
  const found = arr.find((i) => i.type === item.type);
  if (found) {
    found.features.push(...item.features);
  } else {
    arr.push(item);
  }
  return arr;
}, []);

console.log(merged);

---- MODIFIED ----

alternative approach :

const array = [
  {type: 'FeatureCollection', features: [1, 2, 3]},
  {type: 'FeatureCollection', features: [4, 5, 6]},
  {type: 'Test', features: [4, 5, 6]}
]

const merged = array.reduce((obj, item) => {
  if (obj[item.type]) {
    obj[item.type].push(...item.features);
  } else {
    obj[item.type] = item.features;
  }
  return obj;
}, {} as {[key: string]: number[]});

const keys = Object.keys(merged);
const result = keys.map((k) => ({type: k, features: merged[k]}));

console.log(result);

How to Merge Items within an Array of Objects Using Typescript?

Answer №1

Answer №2

Answer №3

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