Comparing one array value with another array

Question

I have an array with values like :

userID: ["55f6c3639e3cdc00273b57a5", 
        "55f6c36e9e3cdc00273b57a6", "55f6c34e9e3cdc00273b57a3"];

$scope.userList : [Object, Object, Object, Object, Object], 

where each object has an ID property of which i am comparing.

I want to compare whether the each userID array value exist in userList array or not.

$scope.userInfo = function(userID) {
    var userDetails = [];
    for (var i = 0; i < $scope.userList.length; i++) {
        (function(i) {
            for (var j = i; j < userID.length; j++) {
                if ($scope.userList[i]._id === userID[j]) {
                    userDetails.push($scope.userList[i]);
                }
            }
        })(i)
    }
    return userDetails;
};

The problem i am facing is for each userID in the array, i want to compare it with all the items in userList object to match.

The above code is not working. Its not comparing each array values with the entire object.

Answer 1

try this

$scope.userInfo = function(userID) {
        var userDetails = [];
        for (var i = 0; i < $scope.userList.length; i++) {       
                for (var j = 0; j < userID.length; j++) {
                    if ($scope.userList[i]._id === userID[j]) {
                        userDetails.push(userID[j]);
                    }
                }       
        }
        return userDetails;
    };

Changes in this lines on if statement

var j = 0;

and

 userDetails.push(userID[j]);

Answer 2

You should try using $filter .

JS:

var userIds = ["55f6c3639e3cdc00273b57a5", 
        "55f6c36e9e3cdc00273b57a6", "55f6c34e9e3cdc00273b57a3"];

$scope.userList = [
    {id: "55f6c3639e3cdc00273b57a5", name: "ASD"},
    {id: "55f6c36e9e3cdc00273b57a6", name: "XYZ"}
  ];

$scope.filteredList = $filter('filter')( $scope.userList, function(user){
  return userIds.indexOf(user.id) != -1;
});

http://plnkr.co/edit/J6n45yuxw4OTdiQOsi2F?p=preview

Answer 3

Instead of using 2 nested loops, convert $scope.userList into an object that has the userID as the key. Then you can loop through your userID array and quickly check if a user with the same key exists in your new object.

By removing the nested loops, the code below runs in linear time instead of n^2, which is beneficial if you have large arrays. And if you store $scope.userList as an object that's keyed by its userId , then you can save even more time by not having to create the index each time the function is run.

$scope.userInfo = function(userID) {

    var userList = {};

    //create object keyed by user_id
    for(var i=0;i<$scope.userList.length;i++) {
        userList[$scope.userList._id] = $scope.userList;
    }

    //now for each item in userID, see if an element exists
    //with the same key in userList created above

    var userDetails = [];
    for(i=0;i<userID.length;i++) {
        if(userID[i] in userList) {
            userDetails.push(userList[userID[i]]);
        }
    }

    return userDetails;
};