Author Archives: Neil Rubens

About Neil Rubens

see http://ActiveIntelligence.org

Food Delivery: Amazon Fresh in Japan

Typically Amazon enters market with a strong offering; however in the case of Amazon Fresh (recently launched in Japan) to me (as analyst and consumer) it is not clear what advantage Amazon Fresh provides in comparison with existing and mature Japanese companies (e.g. … Continue reading

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Online SaaS Peer Assessment / Grading / Polling

Have spent several hours looking for a web-based tool that allows students to vote for each others presentations; by the best free solution was https://www.poll-maker.com/ (p.s. last year spent half a day counting students votes; so decided to automate it this … Continue reading

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java.lang.NoSuchMethodError: com.amazonaws.transform.JsonErrorUnmarshaller: method (Ljava/lang/Class;)V not found

Problem An exception or error caused a run to abort: com.amazonaws.transform.JsonErrorUnmarshaller java.lang.NoSuchMethodError: com.amazonaws.transform.JsonErrorUnmarshaller: method <init>(Ljava/lang/Class;)V not found Solution AWS had some strangely maintained libraries for lambda “com.amazonaws” % “aws-lambda-java-core” % AWSLambdaLibsVersion, “com.amazonaws” % “aws-lambda-java-events” % AWSLambdaLibsVersion, “1.1.0” // https://github.com/aws/aws-lambda-java-libs The … Continue reading

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No compatible version found: @types/react-dom@15.4.2

Solution Was puzzled by the No compatible version found: @types/react-dom@15.4.2 In the end chaning all of the react related vers to “^15.4.1”, did the trick also had an error (2nd one bellow); but that was due to a server already … Continue reading

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React (TypeScript): infinite scroll

Recently I had to use an infinite scroll (lazy loading).  It took me a while to find a solution that worked well for my very simple case (lazy loading items in an infinite scroll fashion).  Hopefully this will save somebody … Continue reading

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ReactJS: Uncaught TypeError: Cannot read property of undefined

Problem You get: Uncaught TypeError: Cannot read property of undefined This is due to react trying to render components that rely on variables that haven’t yet been set (quite a common occurence). Solution You can use conditional rendering shortcut to … Continue reading

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VM54310:600 Uncaught TypeError: _XXXXX2.default is not a constructor

Problem VM54310:600 Uncaught TypeError: _XXXXX2.default is not a constructor Solution need to export default class e.g.: export default class StateController { …         keywords: typescript VM54310:600 Uncaught TypeError: _XXXXX2.default is not a constructor ts js webpack    

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Gradual Migration from JavaScript to TypeScript

Task You have an existing project in which you’d like to use TypeScript. Solution Simply remove the outDir from tsconfig.json, e.g.: { “compilerOptions”: { “allowJs”: false, “outDir”: “./tsDist/”, “module”: “es6”, “target”: “es6”, “experimentalDecorators”: true, “moduleResolution”: “node” }, “exclude”: [ “node_modules”, “tsDist”, … Continue reading

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enabling decorators for mobx

mobx is really great for state management (I prefer it over redux) it is even handier if you can use decorators; to do that its probably easier to use babel 6 (due to some of the issues described here). using npm … Continue reading

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webpack issues

may need to run ‘sudo npm install’ first install missing dependencies with `sudo npm install <DEP>` “` Module parse failed: /home/neil/Dropbox/w540-bak/bitbucket/sa-client-ui/src/app.js Unexpected token (199:40) You may need an appropriate loader to handle this file type. SyntaxError: Unexpected token (199:40) “` … Continue reading

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