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JavaScript in a nutshell

“ In five years I expect that dynamic languages (the successors inspired by today's languages, or today's languages evolved) overtake Java and C++ as the dominant implementation languages in most areas. Moore's law is on our side. ”

—Guido Van Rossum, 2005[1]

“ If you are doing any web development right now, you have to deal with Javascript whether you want it or not. ”

— Blogger

JavaScript is a scripting language with a syntax like C but it has more in common with functional languages.

It is the J in AJAX. It is the basis for all “thick” client models for building apps on the web.

  • AJAX really just means “using the asynchronous calls in Javascript”.
  • XMLHttpRequest is a misnomer - one can use JSON just as well.


Contents

Top 10 one-liners about JavaScript

"JavaScript is the most widely-deployed runtime environment in existence."
"JavaScript is the most successful scripting language ever."
"JavasSript is the most widely deployed language in the world."
"JavaScript: The World's Most Misunderstood Programming Language"[2]
.....
—The Web


"Javascript [became] what nobody expected;
namely a programming language for web applications."
—Lars Bak [3] 


42,889,748 total downloads
— NoScript Firefox add-on [4]


"The Internet breathes JavaScript"
— www.ejscript.org


Javascript has something that neither Python nor Ruby possess - a real spec.
—Blogger


"If you want to scale back power consumption on mobile devices,
V8 can be a good choice."
—Lars Bak, technical lead for the V8 design at Google


"Sure, obj-c is nice but writing your app three times is barbaric."
— John Resig[5]

Top 10 moments in JavaScript history

  • 1995 - JavaScript included in Netscape browser version 2.0B3
  • 1996 - Microsoft's dialect, JScript, was included with IE3
  • 1997 - ECMA-262 (ECMAScript)
  • 1999 - Most recent ECMAScript (Third Edition) - JavaScript 1.5
  • 2000 - DOM Level 2 published
Engine Dialect
Google Chrome V8 JavaScript 1.5
Firefox, SpiderMonkey, Rhino, ... JavaScript 1.8
Apple Safari JavaScript 1.5
MSIE JScript 5.7 (see discrepancies)
.NET JScript.NET 8.0
Adobe Acrobat JavaScript 1.5
  • 2004 Google Mail [6]
  • 2005 Google Maps (JavaScript and JSON)
  • 2005 AJAX (W3C released draft spec for XMLHttpRequest in 2006)
  • 2006 Google Web Toolkit; jQuery
  • 2008 Dojo 1.0

Top 10 JavaScript demos

Top 10 one-liners in JavaScript

  1. javascript:resizeTo(800,600);
  2. javascript:alert(navigator.javaEnabled())
  3. javascript:alert(navigator.appName+navigator.appVersion)
    dojo.isBrowser, dojo.isFF, dojo.isIE, dojo.isSafari, etc
  4. javascript:void((function(){var q=document.getSelection?document:window;q=q.getSelection();if(q=="")q=prompt('Wikipedia:',''); if(q)location.href='http://en.wikipedia.org/w/wiki.phtml?search='+escape(q)})())
    execute
  5. s.replace(RE, t)
    See also: s.match(RE); RE.test(s)
    • s.replace(/^./, String.toUpperCase)
    • s.replace(/^./, function(x) { return x.toUpperCase(); } )
      Exercise: 'abc def'.replace(/\b./g, function(x) { return x.toUpperCase(); } )
  6. javascript:void(document.getElementById('javascriptEnabled').style.display='none');
    JavaScript is not enabled
    make visible
    Cf. dojo.style("javascriptEnabled", "display", "none")
  7. x = !(/[^,:{}\[\]0-9.\-+Eaeflnr-u \n\r\t]/.test(text.replace(/"(\\.|[^"\\])*"/g, ''))) && eval('(' + text + ')');
    — a safe and fast eval for JSON to JavaScript
  8. args=args(); alert(args.x) 
// Parse the query string of a URL (or the incoming URL), returning a hash.
// Note that "&x=" yields "" whereas "&x" yields undefined.
function args(parms) {
  if (!parms) parms = window.location.search.substring(1).split('&');
  var x, ans={};
  for (var i in parms) {
    x = parms[i].split('=');
    ans[x[0]] = x[1];
  }
  return ans;
}


P.S. "This page requires JavaScript" 

<NOSCRIPT>
<H3>This page requires JavaScript</H3> 
</NOSCRIPT>

Top 10 JavaScript language features

  • C or C-like syntax
    expressions, statements, blocks
    () {} ; = , ?: return
    structured programming constructs: if, while, switch, for
    for (var i = 0; i < N; i++) { ... }
    function NAME(ARG, ...) { BODY }
    JavaScript 1.7 uses let for block-level scoping
  • Arrays
    IO=0
    ["a", '"b"', [1,2] ]
  • Objects are associative arrays
    • Object literal notation => JSON
      { name: "John", sons: [ { name: "Junior" } ] }
      kwArgs
  • Functions are first-class objects
    • Every function is a Function object
    • Functions can be defined in several ways:
      1. function f() {}
      2. f = function() {}
      3. f = new Function( [], "" )
  • Constructors are special-purpose functions
    • new F() calls function F with this initially bound to {}, and returns this.
      function Building(name) { this.name = name; }
      function Building(kwArgs) { this.name = kwArgs.name; }
  • Methods
    • Any function can be invoked as a method
      target.f()
  • Inner functions and closures
    Modules -
    • Global = { f: function() {} }
      vs:
    • Module = function() { return { f: function() {} }; }()
  • Regular expressions
  • Delegation
    • Use your selected library's approach to "classes" and inheritance
  • for (x in obj) { ... } loops over all user-defined property names
  • Support for asynchrony in browsers
    • "script tag hack"
    • Asynchronous callbacks (e.g. onclick)
    • XMLHttpRequest

Top 10 peeves about JavaScript

(See JavaScript: The Good Parts for a list of the bad parts.)

  • Global variables
  • No block scope
  • There is no built-in assertion mechanism
    • ideal assertion mechanism cannot be implemented in JS 1.5
      ideal: assert( f() )
      compromise: assert( "f()" )
  • There is no "hasOwnProperty" equivalent of "in" in "for (_ in _)"
    • workaround: for(p in o) { if (o.hasOwnProperty(p) ... }

Top 10 JavaScript libraries and frameworks

  • The "Prototype Javascript framework" is implemented as a single file, typically prototype.js
  • Google Web Toolkit (GWT) — software development in Java
  • jQuery
  • MochiKit
  • MooTools
  • YUI (Yahoo! UI Library)
  • dojo
  • Uize (pron. U-ize)
  • JS.Class — a library that implements Ruby’s core object, module and class system

Top 10 JavaScript tools

  • "Javascript: The Good Parts" by Douglas Crockford
  • Firebug
    • Works adequately in Chrome ..
  • Firebug Lite for other browsers
  • alert()
  • throw()
    e.g. throw("Missing input")
  • JSLint
  • JSONLint

Top 10 news items

  • FF3.1, IE8 and ECMAScript 5 all support JSON
  • "iPhone 3.0 handles JavaScript 3x-10x faster than iPhone 2.1."
  • Server-side JavaScript
  • "Cross-Origin Resource Sharing" — W3C Working Draft 17 March 2009
  • ECMAScript 5 is likely to be published towards the end of 2009

V8 (Google Chrome)

“ Not your mother's JavaScript ”

—  chromeexperiments.com [9]


google_chrome_benchmark_overall.PNG
[10]


tracemonkey-3.png [11] [12]


"Assorted benchmarks" from August, 2008.


engine-perf.gif

2008/09/19

Other Top 10 lists

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