I have a use case wherein I have to compare two elements of an array and display the similar elements along with the index. Suppose, I have two arrays say,

var array1 = ["One", "Two", "Three"];
var array2 = ["Four", "One", "Five"];

I want the output to be as follows:

array1 
One - 1
array2
One - 2

I have written the below code snippet to find out the similar elements in both the arrays but unable to proceed on the above.

const filteredArray = array1.filter(value => array2.includes(value));

Please help.

CodePudding user response：

• Using Array#reduce, iterate over array1 while updating the resulting list of common items having the value, index in array1, and index in array2
• In each iteration, using Array#findIndex, get the index of the current value in array2, if it exists, push a new item to the resulting array.

const 
  array1 = ["One", "Two", "Three"],
  array2 = ["Four", "One", "Five"];

const filteredArray = array1.reduce((commonItems, value, index1) => {
  const index2 = array2.findIndex(e => e === value);
  if(index2 >= 0) {
    commonItems.push({ value, index1, index2 });
  }
  return commonItems;
}, []);

console.log(filteredArray);

CodePudding user response：

Solution with basic for loops:

var array1 = ["One", "Two", "Five"];
var array2 = ["Four", "One", "Five"];

for (let i = 0; i < array1.length; i  ) {
  for (let j = 0; j < array2.length; j  ) {
      if (array1[i] == array2[j]) {
         console.log("array1");
         console.log(array1[i]   " - "   (i   1));
         console.log("array2");
         console.log(array2[j]   " - "   (j   1));
     }
  }
}

Output :

array1
One - 1
array2
One - 2
array1
Five - 3
array2
Five - 3

CodePudding user response：

Clarification : How for array2 it should be One - 2 ? As One is in 0th index in array1

As per my understanding, You can simply achieve this by using Array.forEach() along with the Array.indexOf() method.

Live Demo :

var array1 = ["One", "Two", "Three"];
var array2 = ["Four", "One", "Five"];

array1.forEach(item => {
  if (array2.indexOf(item) !== -1) {
    console.log(item, array2.indexOf(item));
  }
});

array2.forEach(item => {
  if (array1.indexOf(item) !== -1) {
    console.log(item, array1.indexOf(item));
  }
});

CodePudding user response：

What I would do if needed the index is

1. Check 2 arrays to see if they contain the same element
2. Check the indexOf() on each array for that value.

// Set values
const array1 = ["one", "two", "three"];
const array2 = ["three", "five", "four"];

// Find duplicates
const duplicates = array1.filter((item) => array2.includes(item));

const findDiffIndexs = (values, arr1, arr2 ) => {
  const indexes = [];
  
  values.forEach((value) => {
    const index1 = array1.indexOf(value);
    const index2 = array2.indexOf(value);
    
    const label = `Value: '${value}' is found in array1[${index1}] & array2[${index2}]`;
    
    indexes.push(label);
  });
  
  return indexes;
}

if (duplicates) console.log(findDiffIndexs(duplicates, array1, array2));

CodePudding user response：

You can do it in this way & store it in an object

var array1 = ["One", "Two", "Three"];
var array2 = ["Four", "One", "Five"];
let obj={ array1:[],array2:[] }

array1.filter((value,i) => {
  if(array2.indexOf(value) !== -1){
    console.log('value',value, array2.indexOf(value))
    obj["array1"].push(`value - ${i   1}`)
    obj["array2"].push(`value - ${array2.indexOf(value)   1}`)
  }
});

console.log(obj)

Output

{ array1: [ 'value - 1' ], array2: [ 'value - 2' ] }