Comparing two Arrays and return the duplicates

Question

I have two arrays and I would like to compare them and return all the values that are on both, even if they repeat.

const correctValue = ['0', '1'];
const actualValue = [
    ['0', '2', '0', 'E', '1', '1', 'u', '0', '1', '0', ':', '1'],
    ['0', '0', '1', 'u', '0', '}', '1', 'l', '1', '1', '1', '˜'],
    ['x', 'k', 'e', '2', '|', '[', 'z', '8', 's', 'd', '2', '5'],
    ['r', '8', '6', ']', '2', '6', 'H', ';', 'Á', 'l', 'm', '?'],
    ['Y', '0', '0', '1', '1', '7', '1', '.', '0', 'v', '0', '1']
];

Please provide what have you done till now?. Also provide sample input and expected output — Ashish, Dec 20 '18 at 12:19
Do you mean intersection? Then your question might already be answered under https://stackoverflow.com/questions/1885557/simplest-code-for-array-intersection-in-javascript — schlingel, Dec 20 '18 at 12:22
I only have those two arrays. I would like to create a new array with all the "0" and "1" from the "actualValue" array. — cpp, Dec 20 '18 at 12:25

Abhinav · Answer 1 · 2018-12-20T12:49:30.383

Try this Solution:-

   <!DOCTYPE html>
<html>
<body>




<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
const correctValue = ['0', '1'];
const actualValue = [
    ['0', '2', '0', 'E', '1', '1', 'u', '0', '1', '0', ':', '1'],
    ['0', '0', '1', 'u', '0', '}', '1', 'l', '1', '1', '1', '˜'],
    ['x', 'k', 'e', '2', '|', '[', 'z', '8', 's', 'd', '2', '5'],
    ['r', '8', '6', ']', '2', '6', 'H', ';', 'Á', 'l', 'm', '?'],
    ['Y', '0', '0', '1', '1', '7', '1', '.', '0', 'v', '0', '1']
];

function myFunction() {
var same_values=[];
for(var i=0;i<correctValue.length;i++)
{
    for(var j=0;j<actualValue.length;j++)
   {    
        for(var k =0;k<actualValue[j].length;k++)
           {
             if(correctValue[i]==actualValue[j][k])
              {
                same_values.push(actualValue[j][k])
              }
            }
    }
}
console.log(same_values)
}
</script>

</body>
</html>

Thanks for your answer. I tried it, but its not logging anything — cpp, Dec 20 '18 at 12:38
i have updated the code with HTML template. please try this in a html document or in any editor. — Abhinav, Dec 20 '18 at 12:51

Vladislav Kirilenok · Answer 2 · 2018-12-20T14:50:16.807

0

function compareArrays(arr1, arr2) {
  return arr1.reduce((acc, item) {
    if (arr2.includes(item)) {
      acc.push(item)
    }
    return acc
  },[])
}

Not most efficient solution, but it works
Need to specify if you need only unique values or not
The best will be if you write expected output

edited Dec 20 '18 at 14:50

answered Dec 20 '18 at 12:25

Vladislav Kirilenok

1
3

Thanks for your answer. I tried it but it's giving me a syntax error on the first line, the function line. – cpp Dec 20 '18 at 12:40
Sorry, forgot to name the function, you can try once more – Vladislav Kirilenok Dec 20 '18 at 14:50

Jack Bashford · Answer 3 · 2018-12-20T12:36:26.473

You could use Array.prototype.filter(). Try this:

arr1.filter(e => arr2.includes(e));

Working demo:

 

function duplicate(arr1, arr2) {
   return arr1.filter(e => arr2.includes(e));
}

var duplicates = [];

const correctValue = ['0', '1'];
const actualValue = [
['0', '2', '0', 'E', '1', '1', 'u', '0', '1', '0', ':', '1'],
['0', '0', '1', 'u', '0', '}', '1', 'l', '1', '1', '1', '˜'],
['x', 'k', 'e', '2', '|', '[', 'z', '8', 's', 'd', '2', '5'],
['r', '8', '6', ']', '2', '6', 'H', ';', 'Á', 'l', 'm', '?'],
['Y', '0', '0', '1', '1', '7', '1', '.', '0', 'v', '0', '1']
];

actualValue.forEach(arr => duplicates.push(duplicate(correctValue, arr)))

console.log(duplicates);

It's not returning all the values. The output: [ [ '0', '1' ], [ '0', '1' ], [], [], [ '0', '1' ] ] — cpp, Dec 20 '18 at 12:33

Ashish · Answer 4 · 2018-12-20T12:54:42.827

You can use reduce and filter to achieve what you are doing. In this approach, I am filtering each row in actualValue and concatenating the outputs.

const correctValue = ['0', '1'];
const actualValue = [
['0', '2', '0', 'E', '1', '1', 'u', '0', '1', '0', ':', '1'],
['0', '0', '1', 'u', '0', '}', '1', 'l', '1', '1', '1', '˜'],
['x', 'k', 'e', '2', '|', '[', 'z', '8', 's', 'd', '2', '5'],
['r', '8', '6', ']', '2', '6', 'H', ';', 'Á', 'l', 'm', '?'],
['Y', '0', '0', '1', '1', '7', '1', '.', '0', 'v', '0', '1']];

actualValue.reduce((arr, listData)=> arr.concat(listData.filter(data => correctValue.includes(data))),[])
console.log(output) //["0", "0", "1", "1", "0", "1", "0", "1", "0", "0", "1", "0", "1", "1", "1", "1", "0", "0", "1", "1", "1", "0", "0", "1"]

Comparing two Arrays and return the duplicates

4 Answers4