Global variables in Meteor

Question

I have

var Schemas = {};

Meteor.isClient && Template.registerHelper(\"Schemas\", Schemas);

Schemas.Person = new SimpleSchema({
  fullName: {
    ty         


        

Answer 1

ReferenceError is a Node error. Meteor is a framework on top of Node.

Node has a global scope (aka Node's global variable). This error is thrown by Node (not Meteor) if you try to access an undefined global variable.

Browsers also have a global scope called window, and do not throw ReferenceErrors when undefined variables are accessed.

Here's a pattern I like for adding functionality to a class (it's very Meteor):

/lib/Helpers.js      <-- Helpers for everyone (node+browser)
/server/Helpers.js   <-- Server helpers (node)
/client/Helpers.js   <-- Client helpers (browser)

Consider these implementations:

// /lib/Helpers.js
Helpers = {/* functions */};  // Assigned to window.Helpers and global.Helpers

// /server/Helpers.js
Helpers = _.extend(Helpers, {/*more functions*/}

// /client/Helpers.js
Helpers = _.extend(Helpers, {/*more functions*/}

This is a trivial example. What if I didn't want to worry about load order? Why not _.extend() in /lib/Helpers.js?

// /lib/Helpers.js
// Helpers = {/* functions */};                  // Overwrites...
Helpers = _.extend(Helpers, {/* functions */});  // ReferenceError

Because you'll get a ReferenceError from Node if Helpers isn't defined - specifically the "Helpers" used as an argument. (Node knows to assign Helpers as global.Helpers).

Here are two ways to "fix" this:

1) Assign Helpers to something

// /lib/Helpers.js
// Helpers = Helpers || {}    // would be another ReferenceError
if (typeof Helpers === 'undefined') Helpers = {};
Helpers = _.extend(Helpers, {/* functions */});

2) Use helpers from the global

// /lib/Helpers.js
Helpers = _.extend(global.Helpers, {/* functions */});  // works in node, but...

Both of which suck.

1)'s syntax is horrible.
2) works in node, but there is no global in browsers. So it fails it's purpose.

So I gave up and went back to overwriting it the first time in lib, and looking for runtime errors if anything was overwritten.

If you have a handy cross-browser syntax for this, do comment :-) var something = something || {} something.blah = foo;

Here's some other JS shorthand tips.