Javascript Array Splice without changing the index

问题

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 Index 1 in the array via push.

User1 disconnects and is removed via splice.

NOW User2 becomes Index 0.

User1 reconnects and is given Index 1 via push.

User2 disconnects, and Index 1 is removed which is now User1.

This is of course causing a problem.

So my question is how can I remove the item from the array without the index of the other elements changing? Am I on the wrong track here?

回答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.

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;
}

回答2:

Use delete instead of splice.

> a = ['1', '2', '3']
< Array [ "1", "2", "3" ]

> delete a[1]
< true

> a
< Array [ "1", undefined × 1, "3" ]

> a.length
< 3

回答3:

Another option is to use a javascript object instead of an array.

Something like this:

var users = {};

users[1] = 'user 1';
users[2] = 'user 2';

delete users[1];
alert(users[2]);        // alerts "user 2"
alert(typeof users[1]); // alerts "undefined"

You lose the array length property though, so you'll have to keep track of your max user number yourself.

回答4:

remove array elements without facing re-indexing problem

    var ind=[1,6]; //index positions of elements to remove
    var arr=['a','b','c','d','e','f','g']; // actual array
    var arr2 = arr.filter(function(item,index){
            if(ind.indexOf(index)== -1){
            return true;
    }});

now arr2 is ==========>> ['a','c','d','e','f']

来源：https://stackoverflow.com/questions/17387571/javascript-array-splice-without-changing-the-index

标签

javascript

arrays

indexing