Introduction to Scala JS

Editor's Notes

• #4 Why javascript, why we are bothering to do javascript. beacuse as you know its typical to do web development without javascript. ITs the only language, that's basically supported web browser. So at some point you need javascript code. ITs scripting language, not designed to scale large rich web application
• #5 Typescript compilers that compiles in javascript and add some new features such as type annotations, classes and interfaces. CoffeeScript, Dart Coffee script is very popular and targets javascript. One of the main reason of its popularity to get rid of javascript c like syntax, because some people apparently dislike curly braces and semicolon very much. CoffeeScript is inspired by Ruby, Python and Haskell. Google created Dart as a replacement of Dart. They are hoping that one day they will replace javascript. Parenscript, Emscripten, JSIL, GWT. Js.scala
• #6 Scala- an acronym for “Scalable Language”. a careful integration of object-oriented and functional language concepts.Scala runs on the JVM. . scala.js supports all of scala language so it can compile entire scala standard library.
• #7 compiles Scala code to JavaScript, allowing you to write your web application entirely in Scala!. Scala.js compiles full-fledged Scala code down to JavaScript, which can be integrated in your Web application. It provides very good interoperability with JavaScript code, both from Scala.js to JavaScript and vice versa. E.g., use jQuery and HTML5 from your Scala.js code.Since scala as a language and also its library rely on java standard library, so it is impossible to support all of scala without supporting some of java. hence scala.js includes partial part of java standard library , written in scala itself If you are developing rich internet application in scala and you are using all goodness of scala but you are sacrificing javascript interoperability, then you can use scala.js , a scala to javascript compiler. So that you can build entire web application in scala. A javascript backend for scala
• #8 Now-a days interoperability between statically typed and dynamically typed is getting demanded day by day that's why many statically typed languages are targeting javascript. statically typed means, when a type of variable is known at compile time. In dynamically typed means, when a type of variable is interpreted at run time. interoperability with object oriented and functional features of javascript is essential but existing language has poor support for this. But scala.js interoperatibility system is based on powerful for type-directed interoperability with dynamically typed languages. It accommodates both the functional and object oriented features of scala and provides very natural interoperability with both language. It is expressive enough to represnt Dom, jquery in its statically and dynamically typed language. Scala has a very powerful type system with unique combination of features:traits, genrics, implicit conversion, higher order function and user defined dynamic type. As a functional and object-oriented language, its concepts are also very close to JavaScript, behind the type system: no static methods
• #9 its a tool for making javascript download and run faster. its a true compiler for javascript. instead of compiling form source code to javascript, it compiles javascript to better javascript. it parses your javascript, anlyze it, optimize code , remove dead code. it also checks syntax, variable reference.
• #10 its a tool for making javascript download and run faster. its a true compiler for javascript. instead of compiling form source code to javascript, it compiles javascript to better javascript. it parses your javascript, anlyze it, optimize code , remove dead code. it also checks syntax, variable reference.
• #11 its a tool for making javascript download and run faster. its a true compiler for javascript. instead of compiling form source code to javascript, it compiles javascript to better javascript. it parses your javascript, anlyze it, optimize code , remove dead code. it also checks syntax, variable reference.
• #12 Number and characters have same semantices on JVM except 4 exceptionSince JavaScript doesn't have a native float type, we sometimes represent Floats using doubles/numbers, rather than with lower-precision 32-bit floatsUnlike the JVM where dividing an integer type by 0 throws an exception, in Scala.js integer division by 0 is undefined. Instance tests (and consequently pattern matching) on any of Byte, Short, Int, Float, Double are based on the value and not the type they were created with. Calling toString on a Float or a Double that holds an integral value, will not append ".0" to that value. This is due to how numeric values are represented at runtime in Scala.js
• #13 scala.Unit is represented using JavaScript's undefined. Therefore, calling toString() on Unit will returnundefined rather than (). JavaScript regular expressions are slightly different from Java regular expressions. The support for regular expressions in Scala.js is implemented on top of JavaScript regexes.
• #14 When writing an application with Scala.js, it is expected that the main application logic be written in Scala.js, and that existing JavaScript libraries are leveraged. Calling JavaScript from Scala.js is therefore the most important direction of interoperability. Because JavaScript is dynamically typed, it is possible to call JS libraries in a dynamically typed way. However, it is also possible to interop with static types, for better leveraging of Scala.The package scala.scalajs.js (code on GitHub) contains static type definitions for all the types,hese types have all the fields and methods available in the JavaScript API.
• #15 Scala.js provides two syntaxes for creating JavaScript objects in a literal way.
• #16 By default, Scala.js classes, objects, methods and properties are not available to JavaScript. Entities that have to be accessed from JavaScript must be annotated explicitly as exported. The @JSExport annotation is the main way to do this.
• #19 This will perform fast Scala.js-specific optimizations and write the resulting code to a single JavaScript file. You can now use this JavaScript file in your HTML page or in whatever way you like. The resulting file in the target folder will have the suffix -fastopt.js.This is for development purpose.
• #20 To make the resulting JavaScript even smaller (and usually faster as well), the sbt plugin integrates the Google Closure Compiler under the so-called full-optimizations.This will call the Google Closure Compiler on the result of the fast-optimizations stage. Note that this can take a while and is therefore not recommended in the development cycle. The resulting file in the target folder will have the suffix -opt.js. This is for production
• #21 This will perform fast Scala.js-specific optimizations and write the resulting code to a single JavaScript file. You can now use this JavaScript file in your HTML page or in whatever way you like. The resulting file in the target folder will have the suffix -fastopt.js.This is for development purpose.
• #22 If you want the code which is used to run the main class to be written to a file, you can set ScalaJSKeys.persistLauncher := true. Note that this will require your main class to be either unique or explicitly set (mainClass := Some(<name>)). The resulting file in the target folder will have the suffix -launcher.js.
• #23 Piyush Mishra