The Tale of JavaScript

The Tale of JavaScript. I mean ECMAScript. Douglas Crockford Yahoo! Inc.

HyperCard types • Stack: contains backgrounds and cards • Background: an image and buttons and fields • Card: a background and buttons and fields • Button: text and/or image • Field: text

HyperTalk on mouseUp put "100,100" into pos repeat with x = 1 to the ¬ number of card buttons set the location of card ¬ button x to pos add 15 to item 1 of pos end repeat end mouseUp

HyperCard • Stacks of cards containing images, buttons, and text fields. • Didn’t anticipate color. • Didn’t anticipate text links. • Didn’t anticipate networking. • A decade later, cards would become pages.

World Wide Web Simple documents with text links.

Java Scheme Self LiveScript

Java Scheme Self LiveScript JavaScript

Java Scheme Self LiveScript JavaScript ECMAScript

Netscape self destructs! Microsoft abandons Internet Explorer in favor of Avalon.

“Another software technology will come along and kill off the Web, just as it killed News, Gopher, et al. And that judgment day will arrive very soon -- in the next two to three years.” George F. Colony Chairman of the Board and CEO Forrester Research, Inc. [2000] http://web.archive.org/web/20001019084041/http://www.forrester.com/ER/Marketing/1,1503,214,FF.html

Microsoft’s Ajax JScript High fidelity clone of JavaScript. Generalized document model All elements are scriptable. XMLHttpRequest Microsoft declared victory and left the field. The Browser War is over.

AJAX! The Web blindsides Microsoft for the second time.

JavaScript should have died with Netscape. The Ajax Revolution succeeded because of the goodness of JavaScript.

With Ajax, the source of innovation shifted from the web makers to the web developers. Ajax libraries.

A small amount of JavaScript can transform the DOM (one of the world’s awfullest APIs) into something pleasant and productive. Ajax libraries are fun and easy to make.

The World’s Most Popular Programming Language

The World’s Most Popular Programming Language The World’s Most Unpopular Programming Language

Reasons to Hate JavaScript • It has bad parts. • The DOM is awful. • It isn’t Java, C#, C++, Python, … • It didn’t die.

There are reasons to like JavaScript It has good parts.

It scales from beginners to masters.

Number

Number • Only one number type No integer types • 64-bit floating point • IEEE-754 (aka “Double”)

JavaScript doesn’t have int a > 0 b > 0 c = a + b; • Possible results: c < a c < b

Associative Law does not hold (a + b) + c === a + (b + c) • Produces false for some values of a, b, c. • Integers under 9007199254740992 (9 quadrillion) are ok. 9007199254740992 === 9007199254740992 + 1

Decimal fractions are approximate a = 0.1; b = 0.2; c = 0.3; a + b === c false (a + b) + c === a + (b + c) false

Object

All values are objects Except null and undefined.

An object is a dynamic collection of properties. Every property has a key string that is unique within that object.

Get, set, and delete • get object.name object[expression] • set object.name = value; object[expression] = value; • delete delete object.name delete object[expression]

You don’t care about an object’s lineage. You care only about the character of its contents.

An object can inherit from another object. Prototypal inheritance. Differential inheritance. Delegation. Class free.

It is easy to build classical systems using the prototypal system. The prototypal system as more expressive power.

Object Literal Inspiration for JSON.

Boolean true false

String Immutable. Unicode.

Date The Date function is based on Java’s Date class. It was not Y2K ready.

RegExp //([^x00-x1f]|[([^x00-x1f]|[^x00-x1f/])*]|[^x00-x1f/[])+/[gim]*/

Loose Typing

Function Scheme’s lambda

Functions are first-class objects, lexically scoped. Much richer than instance-class-package.

JavaScript is a functional language with dynamic objects and familiar syntax.

JavaScript is especially effective in an event-driven application model.

Programs in JavaScript can be significantly smaller than equivalent programs in other languages. But you must learn to think in JavaScript.

The most effective way to make JavaScript a better language is to remove the bad parts. JSLint.com

ECMAScript • 1999 Third Edition ES3 • 2009 Fifth Edition ES5 – Default – Strict • For the short term, work in the intersection of ES3 and ES5/Strict • For the long term, work with ES5/Strict. • Avoid ES5/Default.

What’s next?

A better target for compilation? JavaScript has become the world’s virtual machine.

An intermediate representation?

Macros?

Threads?

More like _______?

Security? XSS et al

Because of its lambda nature, JavaScript is already close to being an object capability language. It moved closer in ES5/strict. This move should be completed in the next edition.

Mashups! Components representing various interests can work cooperatively for the benefit of the user without compromising each other or the user.

The Last Remaining Problem: The DOM.

HTML5 A big step in the wrong direction.

Ajax has become the dominant application platform. But there is a problem.

The Ajax community has mined all of the latent potential of the 20 th Century browser platform. To go forward we need better browsers.

The Internet Explorer 6 Problem • For many years IE6 was the very best web browser in the world. • More recently, IE6 has become the worst web browser in the world. (If you don’t include Netscape, etc.)

IE6 is fading very slowly. It is hanging on because we are allowing it to hang on.

There are more obsolete copies of IE in use than Opera, Safari, and Chrome combined. It might be years before you can safely and conveniently use all of this new stuff.

We need new support from the new browsers. But we cannot make effective use of the new facilities & support IE6.

IE6 MUST DIE!

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The Tale of JavaScript

by Douglas Crockford on Mar 17, 2010

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