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.

The inner loop is only starting from the outer loop position (for (var j = i;....) - I doubt thats what you intended to do — Jamiec
– Jamiec, Commented Sep 15, 2015 at 13:10
I can't see any reason for the IIFE in the middle of that loop. — T.J. Crowder
– T.J. Crowder, Commented Sep 15, 2015 at 13:10

FuzzyTree · Accepted Answer · 2015-09-15 13:26:12Z

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;
};

Ramesh Rajendran · Accepted Answer · 2015-09-15 13:11:15Z

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]);

Imab Asghar · Accepted Answer · 2015-09-15 13:25:21Z

1

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

edited Sep 15, 2015 at 13:25

answered Sep 15, 2015 at 13:20

Imab Asghar

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