Discover similarities between two arrays

Question

Discover similarities between two arrays

My goal is to compare two arrays and generate a JSON array marking true if there's a match and false if there isn't. The second array will always have values that match some from the first, and it will be smaller as it's derived from the first array.

let firstArray = ["One", "Two", "Three", "Four", "Five"];
let secondArray = ["Three", "Four"];
let jsonArray = [];

The desired JSON array looks like this:

[
  {
    "name": "One",
    "matched": false
  },
  {
    "name": "Two",
    "matched": false
  },
  {
    "name": "Three",
    "matched": true
  },
  {
    "name": "Four",
    "matched": true
  },
  {
    "name": "Five",
    "matched": false
  }
]

Usually, I would use a loop like this:

firstArray.forEach(firstElement=>{
    secondArray.forEach(secondElement=>{
        if(firstArray.indexOf(secondElement)>=0){
            jsonArray.push({'name': secondElement, 'matched': true});
        }else{
            jsonArray.push({'name': secondElement, 'matched': false});
        }
    });
});

However, this method results in duplicate entries in the JSON array where the name matches but the matched value differs.

I feel like I'm overcomplicating something quite straightforward.

javascript arrays typescript match

Answer 1

Answer №1

To achieve the desired result, you can utilize the map function along with the includes helper.

let firstArray = ["One", "Two", "Three", "Four", "Five"];
let secondArray = ["Three", "Four"];
let jsonArray = [];

jsonArray = firstArray.map(i => {
   return { 'name': i, 'matched': secondArray.includes(i) };
});

console.log(jsonArray);

Answer 2

To achieve the desired result, you can utilize the map function along with the includes helper.

let firstArray = ["One", "Two", "Three", "Four", "Five"];
let secondArray = ["Three", "Four"];
let jsonArray = [];

jsonArray = firstArray.map(i => {
   return { 'name': i, 'matched': secondArray.includes(i) };
});

console.log(jsonArray);

Answer 3

Answer №2

Many of the solutions provided here involve unnecessary computations, resulting in longer run-times as the array length increases. Test them with arrays exceeding 100k in size for a clear example.

Fortunately, the optimal solution is quite straightforward and operates in O(n):

const firstArray = ["One", "Two", "Three", "Four", "Five"];
const secondArray = ["Three", "Four"];

const map = {};
firstArray.forEach(item => map[item] = false);
secondArray.forEach(item => map[item] === false && (map[item] = true));
const jsonArray = Object.keys(map).map(key => ({ name: key, matched: map[key] }));

Answer 4

Many of the solutions provided here involve unnecessary computations, resulting in longer run-times as the array length increases. Test them with arrays exceeding 100k in size for a clear example.

Fortunately, the optimal solution is quite straightforward and operates in O(n):

const firstArray = ["One", "Two", "Three", "Four", "Five"];
const secondArray = ["Three", "Four"];

const map = {};
firstArray.forEach(item => map[item] = false);
secondArray.forEach(item => map[item] === false && (map[item] = true));
const jsonArray = Object.keys(map).map(key => ({ name: key, matched: map[key] }));

Answer 5

Answer №3

Give this a shot:

  const firstArray = ["One", "Two", "Three", "Four", "Five"];
  const secondArray = ["Three", "Four"];
  const jsonArray = [];
  firstArray.forEach(firstElement => {
        if(secondArray.includes(firstElement)){
            jsonArray.push({'name': firstElement, 'matched': true});
        } else {
            jsonArray.push({'name': firstElement, 'matched': false});
        }
 });

Hopefully, this code will do the trick for you

Answer 6

Give this a shot:

  const firstArray = ["One", "Two", "Three", "Four", "Five"];
  const secondArray = ["Three", "Four"];
  const jsonArray = [];
  firstArray.forEach(firstElement => {
        if(secondArray.includes(firstElement)){
            jsonArray.push({'name': firstElement, 'matched': true});
        } else {
            jsonArray.push({'name': firstElement, 'matched': false});
        }
 });

Hopefully, this code will do the trick for you

Answer 7

Answer №4

We can utilize the

Array.prototype.includes()

method to verify the presence of an element within an array

let primaryArray = ["One", "Two", "Three", "Four", "Five"];
let secondaryArray = ["Three", "Four"];
let resultArray = [];

primaryArray.forEach(value => {
    if (secondaryArray.includes(value)) {
        resultArray.push({
            'name': value,
            'matched': true
        })

    } else {
        resultArray.push({
            'name': value,
            'matched': false
        })
    }

})

console.log(resultArray);

Answer 8

We can utilize the

Array.prototype.includes()

method to verify the presence of an element within an array

let primaryArray = ["One", "Two", "Three", "Four", "Five"];
let secondaryArray = ["Three", "Four"];
let resultArray = [];

primaryArray.forEach(value => {
    if (secondaryArray.includes(value)) {
        resultArray.push({
            'name': value,
            'matched': true
        })

    } else {
        resultArray.push({
            'name': value,
            'matched': false
        })
    }

})

console.log(resultArray);

Answer 9

Answer №5

Utilize the find method to verify if an element exists

firstArray.forEach(secondElement=>{
  let exists = secondArray.find((item) => item === secondElement);
  if(exists){
    jsonArray.push({'name': secondElement, 'matched': true})
  }else{
    jsonArray.push({'name': secondElement, 'matched': false})
  }
});

View Demo

Answer 10

Utilize the find method to verify if an element exists

firstArray.forEach(secondElement=>{
  let exists = secondArray.find((item) => item === secondElement);
  if(exists){
    jsonArray.push({'name': secondElement, 'matched': true})
  }else{
    jsonArray.push({'name': secondElement, 'matched': false})
  }
});

View Demo

Answer 11

Answer №6

There are two ways to achieve this.

Method 1:

let list1 = ['apple','banana','cherry','date'];

let list2 = ['banana','date'];
let commonList = [];

list1.forEach( item => {
    if(list2.indexOf(item) != -1){
      commonList.push(item);
    }
});

console.log(commonList);   //commonList contains common items

Method 2: Utilize Underscore.js intersection functionality

Start by importing underscore:  
import * as _ from 'underscore';`  

Then use the intersection method to find the common items.  
commonList = _.intersection(list1, list2);

console.log(commonList);   //commonList contains common items

Answer 12

There are two ways to achieve this.

Method 1:

let list1 = ['apple','banana','cherry','date'];

let list2 = ['banana','date'];
let commonList = [];

list1.forEach( item => {
    if(list2.indexOf(item) != -1){
      commonList.push(item);
    }
});

console.log(commonList);   //commonList contains common items

Method 2: Utilize Underscore.js intersection functionality

Start by importing underscore:  
import * as _ from 'underscore';`  

Then use the intersection method to find the common items.  
commonList = _.intersection(list1, list2);

console.log(commonList);   //commonList contains common items

Discover similarities between two arrays

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

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