Find The First Matching Value When Comparing Two Arrays Javascript

I'm trying to find a match between the breeds array and the dogs array. How can I return the first match that is found. This is what i have that doesn't seem to work and I cant qui

Solution 1:

You're returning false on the first non-match, whereas you should continue iterating.

move the return "no match" to after everything has been iterated through.

jsfiddle

You can alternatively also use the indexOf here:

function findTheBreed(dogs) {
    var breeds = ["terrier", "mix", "lab", "hound"];
    for(let i = 0; i < dogs.length; i++) {
      if(breeds.indexOf(dogs[i]) != -1){
      return dogs[i];
    }
  }   
  return "no match";
}

jsfiddle

One other (in my opinion the best) route would be to use the Array.filter functionality and retrieve the entire array of matches.

  var breeds = ["terrier", "mix", "lab", "hound", "snickerdoodle"];
    var filtered = breeds.filter(
    function (elem) {
      return dogs.indexOf(elem) != -1
    }
  );
  return filtered;

jsfiddle

Solution 2:

It would be simpler to turn one array into a dictionary and do a direct lookup.

For example, if dog is turned into a dictionary

var dictionary = {};
for(var i=0;i<dogs.length;i++){
  dictionary[dogs[i]] = true;
}

for(var i=0;i<breeds.length;i++){
  if(dictionary[breeds[i]] === true) return true; //found match
}

Solution 3:

Or shorter:

var findtheBreed=dogs=>["terrier","mix","lab","hound"].find(breed=>dogs.find(dog=>dog===breed))||"no match";

alert(findtheBreed(["pug","husky","hound","poodle"]));

http://jsbin.com/mubatiyebo/edit?console

using Array.prototype.find , Arrow functions and the brilliant OR operator...

Solution 4:

To fix your implementation, move the return "no match" out of the loop body to the end of your findTheBreed function.

However, you can find the first match faster - in constant time - by leveraging constant time Set.has lookup:

function match(dogs, breeds) {
  return dogs.find(Set.prototype.has, new Set(breeds));
}

let dogs = ["pug", "husky", "hound", "poodle"];
let breeds = ["terrier", "mix", "lab", "hound"];

console.log(match(dogs, breeds));

Also, I think you should consider renaming your arrays as there is currently no distinction between a dog and a breed. Also, you might consider declaring the breeds as a Set from the beginning on to avoid redundant conversion.

Solution 5:

You're returning out of the function too early. If you want the same data structure, maybe try this:

var dogs = ["pug", "husky", "hound", "poodle"];
function findBreed(dogs) {
    var breeds = ["terrier", "mix", "lab", "hound"];
    for (let i = 0; i < dogs.length; i++){
        var dog = dogs[i];
        var successIdx = breeds.indexOf(dog)
        if (successIdx !== -1){
            return dog
        }

    }
    return "no match"
 }