Category Archives: Uncategorized

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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DynamoDB: An AttributeValue may not contain an empty string (Exception)

Problem com.amazonaws.AmazonServiceException: One or more parameter values were invalid: An AttributeValue may not contain an empty string (Service: AmazonDynamoDBv2; Solution This cryptic message basically says that dynamodb is not able to save fields with empty strings (or null) (a rather … Continue reading

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