Compare 2 items in a javascript or jquery

Question

I will be glad if I can get help with this issue.

I created a set of questions with options for users and the computer to select from using jquery. The selections of the user and that of the computer are stored in 2 different arrays like the one shown below: userSelection = ["a","b","c","a","d"]; computerSelection = ["e","b","a","d","d"];

Now I want to count the items that matched in both selections e.g. items 2 & 5 ("b" and "d") in the example shown above, how can I go about it? I have tried using the "==" and "===" signs to compare but I couldn't solve this. I really will appreciate if I can be pointed in the right direction. I don't mind if the answer is in jquery or javascript. Thanks

Does this answer your question? [How to compare arrays in JavaScript?](https://stackoverflow.com/questions/7837456/how-to-compare-arrays-in-javascript) or https://stackoverflow.com/search?q=%5Bjavascript%5D+compare+array — freedomn-m, Sep 07 '20 at 07:17
No, the order matters and I am not just looking at the value but thanks — Jeshurun2020, Sep 08 '20 at 05:21
Hi Jesshurun, welcome to SO! Please consider creating a MRE (https://stackoverflow.com/help/minimal-reproducible-example). Thank you — avia, Sep 19 '20 at 00:10

score 0 · Answer 1 · answered Sep 07 '20 at 07:02

0

The simplest solution is to iterate over one array and see if a value at the same index in the other array is the same - if yes, increment the counter:

const userSelection = ["a","b","c","a","d"];
const computerSelection = ["e","b","a","d","d"];

let count = 0;

userSelection.forEach(function (answer, i) {
  if (computerSelection[i] === answer) {
    count++;
  }
});

console.log(count);

answered Sep 07 '20 at 07:02

Sebastian Kaczmarek

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Hi Sebastian, how do i define 'answer'? – Jeshurun2020 Sep 08 '20 at 05:27
@Jeshurun2020 it is already defined as an argument in the callback. Hit the "Run code snippet" button to see how it works – Sebastian Kaczmarek Sep 08 '20 at 05:46

score 0 · Answer 2 · answered Sep 07 '20 at 07:10

You can use a reduce to check each item and then increase the counter

const userSelection = ["a","b","c","a","d"];
const computerSelection = ["e","b","a","d","d"];

const count = userSelection.reduce((counter, item, index) => item === computerSelection[index] ? ++counter : counter, 0);

console.log(count);

If the order doesn't matter:

const userSelection = ["a","b","c","a","d"];
const computerSelection = ["e","b","a","d","d"];

const count = userSelection.reduce((counter, item, index) => computerSelection.includes(item) ? ++counter : counter, 0);

console.log(count);

Thanks Reyno but the order matters. The item has to match an equivalent item. — Jeshurun2020, Sep 08 '20 at 05:22

score 0 · Answer 3 · answered Sep 07 '20 at 07:50

=== and == will check if the two object are the same, ans most of the time it can be read as 'are they the same object in memory':

x = [1,2];
y = [1,2];

console.log(x==y);  // false
console.log(x===y); // false
console.log(x===x); // true

what you can do is create a function that define the equality condition for the two objects: in case of array, if the elements match (and in your use case, the order matters):

userSelection = ["a","b","c","a","d"]; 
computerSelection = ["e","b","a","d","d"];

function checkSelections(user, computer){
  return computer.filter(function(item, i){
    return user[i] === item;
   });
  }
  
  console.log(checkSelections(userSelection, computerSelection));

Compare 2 items in a javascript or jquery

3 Answers3