Copyright © 2012-2013 by Object Computing, Inc. (OCI). All rights reserved.

JavaScript Grievancescommon complaints

about JavaScript

Seinfeld Festivus Airing of Grievanceshttp://www.youtube.com/watch?v=xoirV6BbjOg

JS GrievancesCopyright © 2012-2014 by Object Computing, Inc. (OCI). All rights reserved. 10 -

Assessment Key

E - Addressed by EcmaScript 6 (ES6)

D - Doesn’t really happen in practice

L - Caught by Linting tools (JSLint/JSHint) and/or ES5 strict mode

P - Personal preference

R - Real problem

Y - You can easily learn how to deal with this

2

JS GrievancesCopyright © 2012-2014 by Object Computing, Inc. (OCI). All rights reserved. 10 -

Crockford’s Bad Parts ...

Implied globals (E, L)assign to a variable without a var and it becomes global

can’t do in strict mode

in ES6, use let instead of var

Scope (E, Y)variables are scoped to a function body or they are global

no block scope in things like if statements and loops (see let in ES6)

CoffeeScript and Node.js provide file/module-scoped variables

Semicolon insertion (D, L)semicolons are optional

when omitted, they are automatically inserted, sometimes not where intended

hard to get wrong though

3

JS GrievancesCopyright © 2012-2014 by Object Computing, Inc. (OCI). All rights reserved. 10 -

... Crockford’s Bad Parts ...

Reserved words (L)many aren’t currently used, but reserved for possible future use

don’t have to memorize them; let a lint tool warn you

Unicode (E, D)uses UTF-16 characters, not UTF-8, and string methods expect only 2-byte characters, not 4

characters in all modern languages only require 2 bytes

typeof (Y)

typeof null === 'object' and typeof [1, 2, 3] === 'object'

Numbers (E, D)all are represented by a double; no integer type,but can accurately represent up to 53 bitswhich is large enough for almost all uses

4

JS GrievancesCopyright © 2012-2014 by Object Computing, Inc. (OCI). All rights reserved. 10 -

... Crockford’s Bad Parts

Arrays (E, D)represents arrays as objects where keys are string versions of indexes

a potential performance issue; but not typically

ES6 adds typed arrays of numbers

Falsy values (Y)false, undefined, null, 0, NaN and ""are all treated as false in boolean contexts

everything else is truthy

== vs. === and != vs. !== (L)short forms perform type coercion, long forms do not

eval(code) (D, L)need to be careful about source of code

5

JS GrievancesCopyright © 2012-2014 by Object Computing, Inc. (OCI). All rights reserved. 10 -

More Complaints ...

Implicit type coercions (D, L)Google “Gary Bernhardt WAT”

Verbose function keyword (E, R)

can use arrow functions in ES6

Object keys must be strings (E, R) can use Map and Set collections in ES6

No fancy collections (D, E, R)like sets and maps, only Array and Object

can use Map and Set collections in ES6

6

JS GrievancesCopyright © 2012-2014 by Object Computing, Inc. (OCI). All rights reserved. 10 -

... More Complaints ...

Prototypal inheritance (E, R, Y)many steps to get right

call superclass ctor in subclass ctor

set subclass .prototype to an instance of superclass

set subclass .prototype.constructor to subclass ctor

can use class and extends keywords in ES6

Ability to add/override functions and methods (D)far away from other related definitions

a.k.a. monkey patching

Dynamically typed (P)some prefer static typing

can use TypeScript

7

JS GrievancesCopyright © 2012-2014 by Object Computing, Inc. (OCI). All rights reserved. 10 -

... More Complaints

No require/import/include capability (E, R)each client-side JavaScript file must be referenced from a script tag in HTMLor use something like RequireJS

Node provides CommonJS-style require

ES6 provides modules

Need to learn async programming style (Y)callback functions and avoiding deeply nested calls

Supports mutable things (P)can use ClojureScript

Don’t like braces, parens and semicolons (P)can use CoffeeScript

8

JS GrievancesCopyright © 2012-2014 by Object Computing, Inc. (OCI). All rights reserved. 10 -

Good Parts ...

First-class functionsstore in variables, pass to other functions, return from other functions

a necessary feature for functional programming

Closuresfunctions capture data in the scope where they are defined

Anonymous functions

Functions are objectscan attach properties with any kind of value, even other functions

9

JS GrievancesCopyright © 2012-2014 by Object Computing, Inc. (OCI). All rights reserved. 10 -

... Good Parts ...

Objects are like mapscan add arbitrary properties whose values are data and functions

JSON serializationJSON.stringify(value) and JSON.parse(string)

JavaScript experience carries over toserver-side programming using Node.js

Can use CoffeeScript, ClojureScript and other languagesthat compile to JavaScript instead

10

JS GrievancesCopyright © 2012-2014 by Object Computing, Inc. (OCI). All rights reserved. 10 -

... Good Parts

JavaScript IS THE ONLY PROGRAMMING LANGUAGE SUPPORTED BY ALL POPULAR WEB BROWSERS!

11

JS GrievancesCopyright © 2012-2014 by Object Computing, Inc. (OCI). All rights reserved. 10 -

Stop the Hate!

Typically Twitter commentsOH: JavaScript sucks ... ha, ha, ha!

TIL: JavaScript is lame.

TruthYou can implement nearly any application successfully in nearly any programming language.

Everyone has personal preferences.

There will never be a programming language that is everyone’s favorite.

Hate fragments the community and reduces opportunities for learning from each other.

12