var vs let

const

//cannot change constant
const PI = Math.PI;
PI = 123;

var type = 'grizzly';

while(true){
	var type = 'polar';
	console.log(type);
	break;
}

console.log(type);

polar, polar

polar, grizzly

Error!

let type = 'grizzly';

while(true){
	let type = 'polar';
	console.log(type);
	break;
}

console.log(type);

//great for initiating 3rd library
const moment = require('moment');

Class/Extends vs Function/Prototype

class Bear {
	constructor(){
	   this.type = 'bear';
	}
	says (say){
	   console.log(this.type + ' says ' + say);
	}
}

class Grizzly extends Bear {
	constructor(){
	   super();
       	   this.type = 'grizzly'
	}
}

let bear = new Grizzly();
bear.says('growl');

Output grizzly says growl

Template Strings

let bear = 'grizzly';
let says = 'growls';

console.log(`the ${bear} says ${says}`);

let bears = `
grizzly
polar`;

console.log(bears);

the grizzly says growls

grizzly

polar

Arguments

function bear(type){
  type = type || 'grizzly';
  console.log(type);
}
bear();

function bear(...types){
  console.log(types);
}
bear('polar','grizzly');

['polar','grizzly']

grizzly

function bear(type = 'grizzly'){
  console.log(type);
}
bear();

grizzly

Default Param

Array Parameter

magic global

Import / Export modules to accomplishes:

class TodosCollection extends Mongo.Collection {
  insert(doc, callback) {

    ourDoc.createdAt = ourDoc.createdAt || new Date();
    return super(doc, callback);
  }
}

export default Todos = new TodosCollection('Todos');

Splitting files into modules

// This defines a starting set of data to be loaded if the app is loaded with an empty db.
import './fixtures.js';

// This file configures the Accounts package to define the UI of the reset password email.
import './reset-password-email.js';

// Set up some rate limiting and other important security settings.
import './security.js';

// This defines all the collections, publications and methods that the application provides
// as an API to the client.
import './register-api.js';

//named exports
export const CATURDAY = 'Saturday';
export function catLoaf() {};

//exporting our toys array as catToys
let toys = [ 'yarn', 'feather', 'catnip' ];
export { toys as catToys };

import CATURDAY from '/server/modules/catStuff.js'
import catToys from '/server/modules/catStuff.js'

// Importing a default export. .js is implied on filenames so we 
// can omit it while importing.
import laserPointer123 from './modules/laser-pointer';

// Importing named exports.
import { CATURDAY, catLoaf, catToys } from './modules/cat-stuff';

main.js

/server/modules/catStuff.js

export default function laserPointer() {
  return { color: '#DA5347;'};
} 

const function eatSleepPlayRepeat () {};
export { eatSleepPlayRepeat as default };

/modules/laser-pointer.js

Official test in place of Velocity

///CLIENT/MODULES/CAT-STUFF.TESTS.JS

import { mocha } from 'meteor/avital:mocha';
import { chai, assert } from 'meteor/practicalmeteor:chai';
import laserPointer from './cat-stuff.js';

describe( 'Cat Stuff', () => {
   it( 'draws a laser pointer\'s position as a number', () => {
     let laser = laserPointer();
     assert.typeOf( laser.position, 'number' );
   });
});

meteor test --driver-package avital:mocha --port 3100

Syntax

Community

Performance

Prior to 1.3

Meteor 1.3

What about Atmosphere?