meteor/docs/client/basic/sections/environment.md

{{#template name="basicEnvironment"}}

Environment

{{> autoApiBox "Meteor.isClient"}} {{> autoApiBox "Meteor.isServer"}}

{{#note}} Meteor.isServer can be used to limit where code runs, but it does not prevent code from being sent to the client. Any sensitive code that you don't want served to the client, such as code containing passwords or authentication mechanisms, should be kept in the server directory. {{/note}}

{{> autoApiBox "Meteor.startup"}}

On the server, the callback function will run as soon as the server process is finished starting up. On the client, the callback function will run as soon as the page is ready.

It's good practice to wrap all code that isn't inside template events, template helpers, Meteor.methods, Meteor.publish, or Meteor.subscribe in Meteor.startup so that your application code isn't executed before the environment is ready.

For example, to create some initial data if the database is empty when the server starts up, you might use the following pattern:

if (Meteor.isServer) {
  Meteor.startup(function () {
    if (Rooms.find().count() === 0) {
      Rooms.insert({name: "Initial room"});
    }
  });
}

If you call Meteor.startup on the server after the server process has started up, or on the client after the page is ready, the callback will fire immediately.

{{/template}}