Question

Pardon my complete lack of javascript knowledge in advance, but I can’t seem to find a good example of how to compare two arrays and create another array based the results.

I am attempting to get a list of user accounts from a storage device (uses javascript and handles MOST functions ok), and compare them against a statically created list of “good” users.

Using a switch statement works but I really do not like it, and I’m sure there is a much better way (userList is populated dynamically from the device when I query it):

for (userName = 0; userName < userList.length; userName++) {
    switch (userList[userName]) {
    case 'someuser1':
            printf('Username: ' + userList[userName] + ' is good\n');
            break;
    case 'someuser2':
            printf('Username: ' + userList[userName] + ' is good\n');
            break;
    case 'someuser3':
            printf('Username: ' + userList[userName] + ' is good\n');
            break;
    default:
            printf('Username: ' + userList[userName] + ' is NOT good\n');
    } 
}

I would like to create a third array of “bad users” and compare them against a new array of “good users”, and “found users”. I have started with:

var goodUsers = ["someuser1", "someuser2", "someuser3"];

However I can’t figure out the right combination of multiple for loops, if statements, or otherwise to compare the two and give me an array of the “bad users” that I can loop through and perform actions against.

Any help would be appreciated!

Answer 1

Array’s indexOf method is sweet. It returns the position of an element in the array, if it exists, or returns -1 if it does not.

var goodUsers = ["someuser1", "someuser2", "someuser3"];
var users = ["someuser1", 'basuser'];
var user;

for (var i=0; i < users.length; i++) {
  user = users[i];
  if (goodUsers.indexOf(user) >= 0) {
    console.log(user + ' is a good user');
  } else {
    console.log(user + ' is BAD!!!');
  }
}​

http://jsfiddle.net/qz5fx/1