"JavaScript: The Good Parts" Summary

JavaScript: The Good Parts @jonathanjulian

crockford.com

First, the Bad Parts

globals. optional ; truthy/falsy. scope.

Then, the Good Parts!

functions as objects. loose typing. dynamic objects. literals.

The Bad Parts

globals • x = 1; • var y = 1; • x is in the global namespace • YourAppName.x = 1;

line termination • semi-colons are INSERTED by the parser • optional semi-colons are not a “language feature” • you are not warned

truthy / falsy

=== All of these are false

take advantage • if (x) • if (myobject.propery) • if (myobject.property == null) // no, No, NO! • test for exactly what you want to test for • ...or not • KNOW THE FALSY VALUES undeﬁned, null, false, 0, ‘’, NaN

no block scope • functions create scope • blocks do not

The Good Parts!

functions are objects • can be passed, returned • have scope • have closure

loose typing • no compiler • no type heirarchies

objects are dynamic • members can be added to any object, any time • helpful to attach attributes

object literals • aka JSON • { count: 2, preﬁx: ‘pre_’ } • pass options to functions • JSON as communication • JSON as persistence • etc

Know the bad parts are there...and avoid them

Learn and love the good parts!

tools • FireBug • JSLint • spidermonkey / rhino / v8

takeaway • think about vars and scope • never use == • if (myobject) { • jslint.com

JavaScript is a beautiful language

jonathan.m.julian@gmail.com @jonathanjulian jonathanjulian.com

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"JavaScript: The Good Parts" Summary

by Jonathan Julian on Jul 07, 2009

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"JavaScript: The Good Parts" Summary — Presentation Transcript