meteor - How do I delete or remove Session variables?

Question

Meteor has a Session that provides a global object on the client that you can use to store an arbitrary set of key-value pairs. Use it to store things like the currently selected item in a list.

It supports Session.set, Session.get and Session.equals.

How do I delete a Session name, value pair? I can't find a Session.delete(name) ?

Answer 1

[note: this answer is for Meteor 0.6.6.2 through at least 1.1.0.2]

[edit: updated to also explain how to do this while not breaking reactivity. Thanks to @DeanRadcliffe, @AdnanY, @TomWijsman, and @MikeGraf !]

The data is stored inside Session.keys, which is simply an object, so you can manually delete keys:

Session.set('foo', 'bar')
delete Session.keys['foo']

console.log(Session.get('foo')) // will be `undefined`

To delete all the keys, you can simply assign an empty object to Session.keys:

Session.set('foo', 'bar')
Session.set('baz', 'ooka!')
Session.keys = {}

console.log(Session.get('foo')) // will be `undefined`
console.log(Session.get('baz')) // will be `undefined`

That's the simplest way. If you want to make sure that any reactive dependencies are processed correctly, make sure you also do something like what @dean-radcliffe suggests in the first comment. Use Session.set() to set keys to undefined first, then manually delete them. Like this:

// Reset one value
Session.set('foo', undefined)
delete Session.keys.foo

// Clear all keys
Object.keys(Session.keys).forEach(function(key){ Session.set(key, undefined); })
Session.keys = {}

There will still be some remnants of the thing in Session.keyDeps.foo and Session.keyValueDeps.foo, but that shouldn't get in the way.