Javascriptfor multi disciplinary teams 101

Software Engineer at eBay

Francisco M.S. Ferreira

I present my own opinion and point of view, not the one of my employer.

Why use Java?

• Used everywhere (allegedly)

• Strongly typed language

• Compiled language

• Object Oriented

• Tons of available frameworks

Why use JavaScript?

• Used everywhere (allegedly)

• Strongly typed language

• Compiled language

• Object Oriented

• Tons of available frameworks

Why use JavaScript?

• Used everywhere (allegedly)

• Strongly typed language

• Compiled language

• Object Oriented

• Tons of available frameworks

• Extremely flexible

• It is what runs on the browser!

Typical team

Typical team

Front End Back End

What to expect

• An intro to JavaScripto Simulate Object-Oriented JavaScript

• Packaging / Folder structure

• Known walls new developers hit

o Type safety

o Single threaded system

o Mountain/Piramid of doom.

Java class

Flexibility

Flexibility

My favorite

Private variables

Public functions

Fool proof

Tastes like Java

Step by step

Private variables

Public variables

Private functions

Public functions

Static variables

Static functions

Feels object oriented

No private statics

What about extensions?

What about extensions?

If JS was java…

Let’s apply

What happened there

• When calling apply or call:o The this scope is shared between functions

o Allows multiple inheritances

o Allows order of execution in inheritances

o Directly inherits!

What happened there

• When calling apply or call:o The this scope is shared between functions

o Allows multiple inheritances

o Allows order of execution in inheritances

o Directly inherits!

• It only shares:o ‘public’ functions and variables

What happened there

• When calling apply or call:o The this scope is shared between functions

o Allows multiple inheritances

o Allows order of execution in inheritances

o Directly inherits!

• It only shares:o ‘public’ functions and variables

• It may overwrite methods or get overwritten

Folder naming

Java packages

Folder naming

Java packages JavaScript folders

The three big walls of JS

•JavaScript is not type safe!

•JavaScript is single threaded!

•Lot’s of callbacks with closures!

Javascript !== TypeSafe

If you use:

===

!==

All these

would be

false

Equality of objects is deep

• Recursively compare all elements

• If order is guaranteed:o JSON.stringify && compare JSONs

• Use deep compare function ≈ 120 lines of codeo http://stackoverflow.com/questions/1068834/object-comparison-in-javascript

Single Threaded!

setTimeout

someOtherCode

moreCode

...

aCallback

Mountain of Doom

• Hard to reado And maintain

• Callback hell

• Issueso Memory Leaks

o Error prone

o Hard to debug

o Hard to test

Q & A