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How To Combine Types In Your Node.js Server Tamar Twena-Stern

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Tamar Twena-Stern • Software Engineer - manager and architect • Architect @PaloAltoNetworks • Was a CTO of my own startup • Passionate about Node.js ! • Twitter: @SternTwena

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Tamar Twena-Stern • On Maternity Leave • Have 3 kids • Loves to play my violin • Javascript Israel community leader

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Strongly Typed Languages • Use of programming language types in order to • Capture invariants of the code • Ensure its correctness • Definitely exclude certain classes of programming errors. • Stricter typing rules at compile time • Errors and exceptions are more likely to happen during compilation. • Rules affect variable assignment, return values and function calling.

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JavaScript - Dynamically Typed language • No typing declarations • Runtime error checking • No types information • No return statement

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Problems

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Function Return

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Lets Look At Read File

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Third Party Authentication With Enum

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Demo - Simple Function Call, No Types

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Can You Use This API ?

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Problem Summary • Hard to use existing APIs • Inconsistent types in your code • Type casting is hell • Hard for other developers to read the code and work on top of it

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TypeScript

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TypeScript • Superset of JavaScript • Transpiles to JavaScript • Adds optional static typing • Every JavaScript program is a valid TypeScript program • Can be used to develop Node.js servers

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Transpiles To JavaScript Deploying and running JavaScript files TypeScript compiler create JavaScript files in build folder TypeScript source files

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Demo - Simple Node.js TypeScript Server

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Working With TypeScript In Node.js

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TypeScript Compiler • Standard Microsoft TypeScript compiler • Using the command tsc : • Transpiles all .ts files • Create a build folder with JavaScript source files • Running, debugging and deployment on the build folder

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Ts-node • An executable that we are running • Registers the TypeScript compiler for the relevant TypeScript file extensions. • Transpiling relevant extensions on the fly

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Flow

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Flow • Open source package • developed by Facebook • Static type checker for JavaScript • Works with babel compiler • JavaScript files with flow annotations

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Flow Compiles With Babel Deploying and running JavaScript files Babel compiler create JavaScript files in build folder JavaScript source files with flow annotation

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Simple Node Server With Flow

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Lets Vote For Using Types In Node!

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Basic Usage • Annotate your code with types • Catch errors during “compile” time • No types = plane JavaScript.

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Demo - Basic Usage

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Ease Of Development • Ability to Relate objects to their type origin in the files • Ability to auto complete according to the type origin • Ability to relate type to the file origin • Speeding up development in complex projects

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Demo - Type Relating In The IDE

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Are You Ready To Go Back To Our Problems ?

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Function Return

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Function Return With TypeScript

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Read File With Types

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Third Party Authentication

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Simple Function Call With Types

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Now, Lets Talk About The Challenging Parts

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Code Transpiler • Source to source compiler • Both TypeScript And Flow require using a code transpilar • Typescript - tsc - from Typescript To JavaScript • Flow - babel - traspiles .js files to .js files with no types • The code that you run is not the code that you write

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Adding A Build Step • Can slow development • Every code change requires new build • Need to work with ‘npm watch’ to synchronise every code change • Can cause debugging problems in the IDE

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Production - Using Source Maps • Adding a compilation step -> Source code is different from deployed code • Stack traces from production will appear on the deployed code • Without them - Impossible to debug • Need to use source maps to display stack traces from the original code • Crucial to analyse bugs on different environments (dev/ prod)

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SourceMaps - No Unified Standard • TypeScript: • source-map-support package • Add source map support in tsconfig • Flow + Babel • babel-plugin-source-map-support • Make sure your cloud logging service supports source maps

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Remember This ? It Is Still A Problem

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Tamar Twena-Stern •Twitter: @SternTwena