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 sel

Answer 1

Session.set('name', undefined) or Session.set('name', null) should work.

Answer 2

[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. 

Answer 3

The disadvantage with using delete Session.keys['foo'] is that your template will not hot reload if the session key holds an array. For instance, if you are doing

Template.mytempl.helpers({
    categories: function() {
        return Session.get('srch-categories')
    }
})

and in your template

{{#if categories}}
    {{#each categories}}
        {{this}}
    {{/each}}
{{/if}}

And categories is an array, if you delete the session key, your template will continue to display the last value of categories.