DSLs in JavaScript
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This document discusses Domain Specific Languages (DSLs) and their use in JavaScript. It begins by defining DSLs and providing examples of domain-specific lexicons. It then covers internal and external DSLs, and examples of JavaScript DSLs like JSSpec (for testing) and ActiveRecord.js (for object-relational mapping). The document concludes by discussing lessons learned from building DSLs in JavaScript, such as its lack of namespaces being a challenge but prototypal inheritance and object literals providing opportunities.
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DSLs in JavaScript
- 1. DSLs in JavaScript Nathaniel T. Schutta
- 2. Who am I? • Nathaniel T. Schutta http://www.ntschutta.com/jat/ • Foundations of Ajax & Pro Ajax and Java Frameworks • UI guy • Author, speaker, teacher • More than a couple of web apps
- 3. The Plan • DSLs? • JavaScript? Seriously? • Examples • Lessons Learned
- 4. DS what now?
- 6. Every domain has its own language.
- 7. “Part of the benefit of being "into" something is having an insider lexicon.” Kathy Sierra Creating Passionate Users http://headrush.typepad.com/creating_passionate_users/2006/11/why_web_20_is_m.html
- 8. Three quarter, knock down, soft cut.
- 9. Scattered, smothered, covered.
- 10. Large skim mocha, no whip no froth.
- 13. Expressive.
- 14. Terse.
- 16. Not a new idea.
- 17. Unix.
- 19. Lisp.
- 20. Build the language up...
- 21. Lots of attention today.
- 22. Rails!
- 23. Ruby is very hospitable.
- 24. So are other languages ;)
- 26. Internal.
- 27. Within an existing language.
- 29. Simpler.
- 30. No grammars, parsing, etc.
- 31. Constrained by host language.
- 33. Ruby ;)
- 35. Embedded DSLs.
- 36. External.
- 37. Create your own language.
- 38. Grammars.
- 39. Need to parse.
- 41. Harder.
- 42. More flexibility.
- 44. Tools for creating new languages.
- 45. Internal are more common today.
- 46. Language workbenches - shift afoot?
- 48. Meta Programming System. http://www.jetbrains.com/mps/
- 49. Intentional Programming - Charles Simonyi. http://intentsoft.com/ http://www.technologyreview.com/Infotech/18047/?a=f
- 52. Why are we seeing DSLs?
- 53. Easier to read.
- 54. Closer to the business.
- 55. Less friction, fewer translations.
- 57. “Yesterday, I did a code review. With a CEO... Together, we found three improvements, and a couple of outright bugs.” Bruce Tate Canaries in the Coal Mine http://blog.rapidred.com/articles/2006/08/30/canaries-in-the-coal-mine
- 58. Don’t expect them to write it though!
- 59. Will we all write DSLs?
- 60. No.
- 61. Doesn’t mean we can’t use them.
- 62. General advice on building a DSL:
- 63. Write it as you’d like it to be...
- 64. Even on a napkin!
- 68. http://martinfowler.com/dslwip/ http://weblog.jamisbuck.org/2006/4/20/ writing-domain-specific-languages http://memeagora.blogspot.com/2007/11/ ruby-matters-frameworks-dsls-and.html http://martinfowler.com/bliki/DslQandA.html
- 69. Not a toy!
- 70. JavaScript has been around for a while.
- 71. Many dismissed it as “toy for designers.”
- 72. It’s not the 90s anymore.
- 73. We have tools!
- 75. Ajax.
- 76. Suffers from the “EJB issue.”
- 78. “The Next Big Language” http://steve-yegge.blogspot.com/ 2007/02/next-big-language.html
- 79. Runs on lots of platforms - including the JVM.
- 80. Ruby like?
- 81. “Rhino on Rails” http://steve-yegge.blogspot.com/ 2007/06/rhino-on-rails.html
- 82. Orto - JVM written in JavaScript. http://ejohn.org/blog/running-java-in-javascript/
- 85. JSSpec.
- 87. JSSpec? Really?
- 88. /** * Domain Specific Languages */ JSSpec.DSL = {};
- 89. BDD for JS.
- 90. Like RSpec.
- 91. Not quite as elegant.
- 92. describe('Plus operation', { 'should concatenate two strings': function() { value_of("Hello " + "World").should_be("Hello World"); }, 'should add two numbers': function() { value_of(2 + 2).should_be(4); } })
- 93. value_of?
- 95. Sorry.
- 97. We’d need to modify Object’s prototype.
- 99. Though it’s been done. http://json.org/json.js
- 101. Design choice - consistency.
- 102. describe('Plus operation', { 'should concatenate two strings': function() { value_of("Hello " + "World").should_be("Hello World"); }, 'should add two numbers': function() { value_of(2 + 2).should_be(4); } })
- 103. describe - global defined in JSSpec.js.
- 105. And adds it to an array of specs.
- 106. value_of - global defined in JSSpec.js.
- 107. value_of - converts parm to JSSpec.DSL.Subject
- 110. Added to prototype.
- 111. JSSpec.DSL.Subject.prototype.should_be = function(expected) { var matcher = JSSpec.EqualityMatcher.createInstance(expected,this.target); if(!matcher.matches()) { JSSpec._assertionFailure = {message:matcher.explain()}; throw JSSpec._assertionFailure; } }
- 112. this.target?
- 113. JSSpec.DSL.Subject = function(target) { this.target = target; };
- 114. this in JS is...interesting.
- 115. Why is everything JSSpec.Foo?
- 116. JS lacks packages or namespaces.
- 117. Keeps it clean.
- 118. Doesn’t collide...unless you have JSSpec too!
- 119. Not just a DSL of course.
- 120. Defines a number of matchers.
- 121. Also the runner and the logger.
- 123. Some CSS to make it pretty.
- 124. ~1500 lines of code.
- 125. Clean code.
- 126. Why would you use it?
- 127. Easier to read.
- 128. function testStringConcat() { assertEquals("Hello World", "Hello " + "World"); } function testNumericConcat() { assertEquals(4, 2 + 2); }
- 129. var oTestCase = new YAHOO.tool.TestCase({ name: "Plus operation", testStringConcat : function () { YAHOO.util.Assert.areEqual("Hello World", "Hello " + "World", "Should be 'Hello World'"); }, testNumericConcat : function () { YAHOO.util.Assert.areEqual(4, 2 + 2, "2 + 2 should be 4"); } });
- 130. describe('Plus operation', { 'should concatenate two strings': function() { value_of("Hello " + "World").should_be("Hello World"); }, 'should add two numbers': function() { value_of(2 + 2).should_be(4); } })
- 131. Better? Worse?
- 132. What would you rather read 6 months later?
- 134. ActiveRecord.js
- 135. JavaScript ORM.
- 136. Seriously?
- 137. Yep.
- 138. Let’s you use a DB from JavaScript.
- 139. Client or server ;)
- 140. Gears, AIR, W3C HTML5 SQL spec.
- 142. Some free finder methods.
- 143. Base find method.
- 144. Migrations.
- 145. ActiveRecord.Migrations.migrations = { 1: { up: function(schema){ schema.createTable('one',{ a: '', b: { type: 'TEXT', value: 'default' } }); }, down: function(schema){ schema.dropTable('one'); } } };
- 146. Validations.
- 148. More to come...
- 150. Early stages...
- 153. Objective-J
- 155. JavaScript superset.
- 156. Cheating...kind of.
- 158. Allows for instance methods.
- 159. Parameters are separated by colons.
- 160. - (void)setJobTitle: (CPString)aJobTitle company: (CPString)aCompany
- 161. Bracket notation for method calls.
- 162. [myPerson setJobTitle: "Founder" company: "280 North"];
- 163. Does allow for method_missing. http://cappuccino.org/discuss/2008/12/08/ on-leaky-abstractions-and-objective-j/
- 165. Coffee DSL.
- 166. Lessons learned.
- 167. Viable option.
- 170. Syntax isn’t as flexible.
- 171. Lots of reserved words.
- 172. Freakn ;
- 173. Hello prototype!
- 174. Verbs as first class citizens.
- 175. Object literals.
- 176. DSL vs. named parameters vs. constructor parms.
- 177. new Ajax.Request('/DesigningForAjax/validate', { asynchronous: true, method: "get", parameters: {zip: $F('zip'), city: $F('city'), state: $F('state')}, onComplete: function(request) { showResults(request.responseText); } })
- 178. Fail fast vs. fail silent.
- 179. Method chaining is trivial.
- 180. Context can be a challenge.
- 181. Documentation key.
- 182. PDoc,YUI Doc. https://www.ohloh.net/p/pdoc_org http://developer.yahoo.com/yui/yuidoc/
- 183. JavaScript isn’t a toy.
- 184. Not quite as flexible.
- 185. Plenty of metaprogramming goodness!
- 186. Questions?!?
- 187. Thanks! Please complete your surveys.