JavaScript

By: Daniel Henneberger

ECMAScript v5.1

By: Daniel Henneberger

Introduction Data Types Flow Control Inheritance/Built-in Functions User defined types, Generics Arrays Function methods Quirks Comparison

Prototype-based scripting language Interpreted?

Chrome V8 attempts to compile Java’s Rhino attempts to compile to byte code Mozilla attempts JIT

Garbage Collection – Up to implementer Loosely-typed, First-class functions, dynamic Java-like syntax Two Subsets

Default Language (will be abandon later) Strict Language

Free The word JavaScript must be licensed by Oracle Mozilla has ‘Inventor rights’

Brief

Developed for client-side processing on web

browsers Now capable of other tasks

Web Servers (node.js) Desktop Widgets Inside Applications

Applications

Originally Called LiveScript 1995- Created for Netscape Navigator by Brendan

Eich 1995- Renamed JavaScript

Most likely a marking ploy 1996- Microsoft created Jscript 1998- Formalized to ECMAScript 1998- ISO/IEC 16262 1998- ECMAScript v2 1999- ECMAScript v3

History of JavaScript

1999-2009 – ECMAScript v4 (Abandoned) 2008- Google’s V8 Engine 2009- Node.js created 2009- ECMAScript v5 2010- Test262 created 2011-  ISO/IEC 16262:2011 2011- ECMAScript v5.1

History of JavaScript

2013 – Java 8’s JavaScript Engine (Nashorn) 201? ECMAScript v6

Only strict mode Incompatible syntax Classes Getters/Setters Tamper proof objects Block Scoping

Future of JavaScript

Adobe, Mozilla, Microsoft Later came IBM, Google, Apple, Opera, Dojo,

and Company 100.

ECMAScript Committee

Codename Browser Test262 Fail Percent

Jscript Microsoft Internet Explo. 9 5.2%

SpiderMonkey Firefox 1.5%

Futhark Opera 0.1%

V8 Chrome 0.1%

Implementations

Test262 really important

End of line semicolons optional

Automatically inserted by compiler Excess whitespace and comments are

discarded during lexical analysis Strings can be defined by ' or "

Multiline Strings possible with \

Grammar

Introduction Data Types Flow Control Inheritance/Built-in Functions User defined types, Generics Arrays Function methods Quirks Comparison

var - has functional scoping const null undefined

let has block scoping (ECMAScript v6) let and const to replace var

Usable Types

Undefined - primitive value used when a variable has not been

assigned a value Null - no value Boolean – true/false Number - double-precision 64-bit

NaN, Positive Infinity, Negative Infinity IEEE 754

String - UTF-16 Object

runtime system performs automatic type conversion as needed 1+true=2, null + false = 0, null != false, null == undefined

Type coercion – new Boolean(true);

Internal Types

Introduction Data Types Flow Control Inheritance/Built-in Functions User defined types, Generics Arrays Function methods Quirks Comparison

Flow Control - Sequencing

function test(){ for(var i = 0; i<10; i++){ //doSomething; } return i;}result is 10

if(Expression) Statement else Statement if(Expression) Statement

SwitchStatement: switch (Expression) CaseBlock CaseBlock:

{CaseClause} {CaseClause DefaultClause CaseClause}

CaseClause: case Expression : StatementList Default Clause: default : StatementList

with(Expression) Statement

LogicalORExpression ? AssignmentExpression : AssignmentExpression

Flow Control – Selection

Simple Assignment: = Compound Assignment: op=

*= /= %= += -= <<= >>= >>>= &= ^= |=

Comma Operator ( , )

Flow Control – Expression Evaluation

do Statement while ( Expression ); while ( Expression ) Statement for (ExpressionNoIn; Expression ; Expression )

Statement for ( var VarDeclaration; Expression; Expression)

Statement for ( LeftHandSideExpression in Expression ) Statement for ( var VariableDeclarationNoIn in Expression )

Statement

label, break, continue, (throw, return, ‘normal’)

Flow Control – Iteration

function Identifier ( ParameterList ) { FunctionBody } function ( ParameterList ) { FunctionBody }

function square(y){ this.rslt = y*y;}var x = new square(5);x.rslt;

var square = new Function("a", "b", "return a*b")

Flow Control – Procedural Abstraction

var x = function(y) {   return y * y;};x(5);function square(y){ return y*y;}square(5);var Math = { square: function(y){ return y*y }}Math.square(5);

Object Properties

Flow Control – Procedural Abstraction

Object.defineProperty(o, "a", {value : 37, writable : true, enumerable : true, configurable : true, get : function(){

return bValue; },set : function(newValue){

bValue = newValue; }

});

No optimization for Tail Call Recursion No concurrency

setTimeout(func, delay, [params]) setInterval() new Worker(“something.js”)

Flow Control – Recursion/Concurrency

try / catch try / finally try / catch / finally try {Code} catch ( Identifier ) {Code}

finally {Code}

throw Error, EvalError, RangeError, ReferenceError,

SyntaxError, TypeError and URIError

Flow Control – Exception Handling

Global - variables that are not declared but

are referenced are automatically global Eval

Strict Mode- cannot return variables Creates a new binding

Function function x(){t = 5}; x(); console.log(t) //5 function x(){var t = 5}; x(); console.log(t)

//undef

Execution Context

Introduction Data Types Flow Control Inheritance/Built-in Functions User defined types, Generics Arrays Function methods Quirks Comparison

function Person(){}function Ninja(){}Ninja.prototype = new Person();(new Ninja()) instanceof Person

var o = new Object();o.[[Prototype]] = Foo.prototype;o.Foo();

Prototype Based Inheritance

Number

parseInt() parseFloat() parseInt() isNaN() ifFinite()

eval() Library

Math JSON Date RegExp

Special Characters decodeURI encodeURI

Built-in Functions

Introduction Data Types Flow Control Inheritance/Built-in Functions User defined types, Generics Arrays Function methods Quirks Comparison

user defined typesgenerics

NONE!

Introduction Data Types Flow Control Inheritance/Built-in Functions User defined types, Generics Arrays Function methods Quirks Comparison

new Array([item1, item2, …]) new Array(len) Keys can be integers or strings Can be treated as: Arrays, Queues, Stacks,

Priority Queues, Set No bounds

arr[arr.length] = I;

Arrays

push pop reverse sort sort(function) shift slice splice unshift indexOf every lastIndexOf some(function) forEach(function) map(function) filter(function) reduce(function) reduceRight(function)

Array Operations

x = 42;         // creates the property x on the global objectvar y = 43;     // declares a new variable, ymyobj = {};myobj.h = 4;    // creates property h on myobjmyobj.k = 5;    // creates property k on myobj delete x;       // returns true  (x is a property of the global object and can be deleted)delete y;       // returns false (delete doesn't affect variable names)delete Math.PI; // returns false (delete doesn't affect certain predefined properties)delete myobj.h; // returns true  (user-defined properties can be deleted) with(myobj) {     delete k;   // returns true  (equivalent to delete myobj.k)}  delete myobj;   // returns true 

delete

Introduction Data Types Flow Control Inheritance/Built-in Functions User defined types, Generics Arrays Function methods Quirks Comparison

bind() is powerful

x.bind(this); call() – allows calling inner functions with

current bindings toString()

Built-in Function Functions

Introduction Data Types Flow Control Inheritance/Built-in Functions User defined types, Generics Arrays Function methods Quirks Comparison

Floating point arithmetic IEEE 754

0.1 + 0.2 !== 0.3 A bad choice

All implementations see to behave differently Code not portable

Accidental scoping Global variables

var a = 0 || "4"; a = "4“

Scope hoisting eval()

Quirks

Introduction Data Types Flow Control Inheritance/Built-in Functions User defined types, Generics Arrays Function methods Quirks Comparison

JavaScript Java C Go

Type Loosely Typed

Strongly Typed

Strongly Typed

Strongly Typed

Inheritance

Prototypal Classical Classical Automatic

Multiple Inheritance

No No No Yes

Generics No Yes No No

Pointers No Yes No Yes

Closures Yes No No Yes

Exceptions Yes Yes No Built-in

Threads No Yes Yes Yes

Garbage Collection

Yes Yes No Yes

Semi-Colon Optional

Yes No No Yes

Like JavaScript

100% 30% 30% 40%

“Java and Javascript are similar like Car and Carpet are

similar.” Greg Hewgill

www.ecma-international.org

/publications/files/ECMA-ST/Ecma-262.pdf

References