Changes to JavaScript, Part 1: EcmaScript 5

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Table of contents

Changes to JavaScript, Part 1: EcmaScript 5

EcmaScript 5 Overview

Aren't standards doomed to grow?

Problem: Can’t emulate platform objects

Accessor (getter/setter) properties

Accessor (getter/setter) properties…

Need property attribute control

Property attribute control API

Example: Unobtrusive Convenience Methods

Accessor (getter/setter) properties…

Practical emulation of host objects

ES3 Makes Robustness Too Hard

More Robust Programming in ES5

What’s the Point? Can’t preserve invariants in ES3

Tamper proof objects

Tamper proof points, first try

Tamper proof points, second try

Frozen object builder helper

Tamper proof points

Scoping accident 1: Nested named function expressions

Finding Opportunity in Confusion

Scoping accident 2: Throwing a function

Scoping accident 3: “as if by” initial or current?

Wart exchange: keyword collision

Wart removal: Backchannel

Wart exchange: eval in what scope?

Wart clarifications: Internal“types”

Strict mode: Support Defensive Code

Strict mode: Per script opt-in

Strict mode: Per script or per function opt-in

Nonstrict global object leakage

Nonstrict this-coercion hazards

ES5 functions encapsulated?

ES5-strict functions encapsulated

ES5-nonstrict isn't statically scoped

ES5-strict is statically scoped, but…

But static scoping isn’t lexical scoping

Lexical Scoping just missed ES5 train. How to cope?

Higher order array methods

JSON: S-expressions of the web

Closures don’t capture “this”

Function.prototype.bind() helps

Imperfect Lambda Abstraction in ES5

Remaining fixable ES5 warts

Further Reading

Author: Mark S. Miller, Waldemar Horwat, Mike Samuel

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