Javascript Array Splice without changing the index

Question

I am working on a chat and using an array to hold the users. Here is my problem:

User1 joins and is given Index 0 in the array via push. User2 joins and is given Ind

Answer 1

Instead of removing the items from the array with splice(), why not just set the value to null or undefined?

Then when you're adding a new user, you can just scan through the array to find the first available slot.

javascript arrays are simply lists of items - they're not keyed to a specific key like you might be familiar with in PHP. So if you want to keep the same position in the array, you can't remove other items - you need to keep them, and just mark them as empty.

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You might scan through something like this:

var users = [];
function addUser(user) {
    var id = users.indexOf(null);
    if (id > -1) {
        // found an empty slot - use that
        users[id] = user;
        return id;
    } else {
        // no empty slots found, add to the end and return the index
        users.push(user);
        return users.length - 1;
    }
}
function removeUser(id) {
    users[id] = null;
}