[backend][nodejs] Use express framework instead of http module

backend/nodejs/.gitignore

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+# ---> Node
+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+lerna-debug.log*
+
+# Diagnostic reports (https://nodejs.org/api/report.html)
+report.[0-9]*.[0-9]*.[0-9]*.[0-9]*.json
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+*.lcov
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (https://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (https://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules/
+jspm_packages/
+
+# Snowpack dependency directory (https://snowpack.dev/)
+web_modules/
+
+# TypeScript cache
+*.tsbuildinfo
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Microbundle cache
+.rpt2_cache/
+.rts2_cache_cjs/
+.rts2_cache_es/
+.rts2_cache_umd/
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# dotenv environment variables file
+.env
+.env.test
+
+# parcel-bundler cache (https://parceljs.org/)
+.cache
+.parcel-cache
+
+# Next.js build output
+.next
+out
+
+# Nuxt.js build / generate output
+.nuxt
+dist
+
+# Gatsby files
+.cache/
+# Comment in the public line in if your project uses Gatsby and not Next.js
+# https://nextjs.org/blog/next-9-1#public-directory-support
+# public
+
+# vuepress build output
+.vuepress/dist
+
+# Serverless directories
+.serverless/
+
+# FuseBox cache
+.fusebox/
+
+# DynamoDB Local files
+.dynamodb/
+
+# TernJS port file
+.tern-port
+
+# Stores VSCode versions used for testing VSCode extensions
+.vscode-test
+
+# yarn v2
+.yarn/cache
+.yarn/unplugged
+.yarn/build-state.yml
+.yarn/install-state.gz
+.pnp.*
+
+# Webstorm
+.idea/
+
+# TypeScript
+lib/

backend/nodejs/package.json

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+{
+  "name": "nodejs",
+  "version": "1.0.0",
+  "description": "",
+  "main": "lib/app.js",
+  "scripts": {
+    "test": "ts-mocha -p tsconfig.json src/**/*.spec.ts",
+    "start": "tsc && node lib/app.js",
+    "build": "tsc -p .",
+    "build:live": "nodemon --watch 'src/**/*.ts' --exec \"ts-node\" src/app.ts"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "devDependencies": {
+    "@types/expect": "^24.3.0",
+    "@types/express": "^4.16.1",
+    "@types/mocha": "^8.2.2",
+    "@types/node": "^14.14.37",
+    "mocha": "^8.3.2",
+    "nodemon": "^2.0.7",
+    "ts-mocha": "^8.0.0",
+    "ts-node": "^9.1.1",
+    "tslint": "^5.12.1",
+    "typescript": "^4.2.3"
+  },
+  "dependencies": {
+    "express": "^4.16.4",
+    "random": "^3.0.3",
+    "seedrandom": "^3.0.5",
+    "should": "^13.2.3"
+  }
+}

backend/nodejs/src/app.ts

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+import express from 'express';
+const randomDecision = require("./random-decision")
+
+const app = express();
+const port = 3000;
+
+app.get('/', ((req, response) => {
+    response.send(randomDecision.getRandomChoice());
+}));
+
+app.listen(port, () => {
+    return console.log(`Server is listening on port ${port}`);
+});

backend/nodejs/src/random-decision.spec.ts

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+const assert = require('assert');
+const should = require('should');
+const randomDecision = require('./random-decision');
+
+describe('randomDecision', function () {
+    describe('#getRandomChoice()', function () {
+        it(`should return one of available choices`, function () {
+            randomDecision.getRandomChoice().should.equalOneOf(randomDecision.choices);
+        });
+
+        it('should return the first choice sometimes', function () {
+            const expectedChoice = randomDecision.choices[0];
+            const selectedChoices = new Set();
+            for (let i = 0; i <= 1000; i++) {
+                const decision = randomDecision.getRandomChoice();
+                selectedChoices.add(decision);
+                if (decision === expectedChoice) {
+                    should.ok(decision, 'First choice was found once');
+                    return;
+                }
+            }
+            should.fail(selectedChoices, expectedChoice, 'First choice was never selected');
+        })
+        it('should return the last choice sometimes', function () {
+            const expectedChoice = randomDecision.choices[randomDecision.choices.length - 1];
+            const selectedChoices = new Set();
+            for (let i = 0; i <= 1000; i++) {
+                const decision = randomDecision.getRandomChoice();
+                selectedChoices.add(decision);
+                if (decision === expectedChoice) {
+                    should.ok(decision, 'Last choice was found once');
+                    return;
+                }
+            }
+            should.fail(selectedChoices, expectedChoice, 'Last choice was never selected');
+        })
+    })
+    describe('#getRandomChoice(seed)', function () {
+        it('should always select the same value when the seed is the same', function () {
+            const seed = new Date();
+            const initialDecision = randomDecision.getRandomChoice(seed);
+            for (let i = 0; i <= 1000; i++) {
+                let randomChoice = randomDecision.getRandomChoice(seed);
+                assert.strictEqual(randomChoice, initialDecision);
+            }
+        })
+    })
+})

backend/nodejs/src/random-decision.ts

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+const random = require('random');
+const seedrandom = require("seedrandom");
+
+class Choice {
+    private readonly name: String;
+    constructor(name: String) {
+        this.name = name;
+    }
+
+    toString() {
+        return this.name;
+    }
+}
+
+const choices = [
+    new Choice('A'),
+    new Choice('B'),
+    new Choice('C')
+];
+
+exports.getRandomChoice = (seed = new Date()) => {
+    random.use(seedrandom(seed));
+    return choices[random.int(0, choices.length - 1)];
+}
+
+exports.choices = choices;

backend/nodejs/tsconfig.json

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+{
+  "compilerOptions": {
+    /* Visit https://aka.ms/tsconfig.json to read more about this file */
+
+    /* Basic Options */
+    // "incremental": true,                         /* Enable incremental compilation */
+    "target": "es5",                                /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', or 'ESNEXT'. */
+    "module": "commonjs",                           /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 'es2020', or 'ESNext'. */
+    "lib": ["es6","dom"],                           /* Specify library files to be included in the compilation. */
+    // "allowJs": true,                             /* Allow javascript files to be compiled. */
+    // "checkJs": true,                             /* Report errors in .js files. */
+    // "jsx": "preserve",                           /* Specify JSX code generation: 'preserve', 'react-native', 'react', 'react-jsx' or 'react-jsxdev'. */
+    // "declaration": true,                         /* Generates corresponding '.d.ts' file. */
+    // "declarationMap": true,                      /* Generates a sourcemap for each corresponding '.d.ts' file. */
+    // "sourceMap": true,                           /* Generates corresponding '.map' file. */
+    // "outFile": "./",                             /* Concatenate and emit output to single file. */
+    "outDir": "lib",                                /* Redirect output structure to the directory. */
+    "rootDir": "src",                               /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
+    // "composite": true,                           /* Enable project compilation */
+    // "tsBuildInfoFile": "./",                     /* Specify file to store incremental compilation information */
+    // "removeComments": true,                      /* Do not emit comments to output. */
+    // "noEmit": true,                              /* Do not emit outputs. */
+    // "importHelpers": true,                       /* Import emit helpers from 'tslib'. */
+    // "downlevelIteration": true,                  /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
+    // "isolatedModules": true,                     /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */
+
+    /* Strict Type-Checking Options */
+    "strict": true,                                 /* Enable all strict type-checking options. */
+    // "noImplicitAny": true,                       /* Raise error on expressions and declarations with an implied 'any' type. */
+    // "strictNullChecks": true,                    /* Enable strict null checks. */
+    // "strictFunctionTypes": true,                 /* Enable strict checking of function types. */
+    // "strictBindCallApply": true,                 /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
+    // "strictPropertyInitialization": true,        /* Enable strict checking of property initialization in classes. */
+    // "noImplicitThis": true,                      /* Raise error on 'this' expressions with an implied 'any' type. */
+    // "alwaysStrict": true,                        /* Parse in strict mode and emit "use strict" for each source file. */
+
+    /* Additional Checks */
+    // "noUnusedLocals": true,                      /* Report errors on unused locals. */
+    // "noUnusedParameters": true,                  /* Report errors on unused parameters. */
+    // "noImplicitReturns": true,                   /* Report error when not all code paths in function return a value. */
+    // "noFallthroughCasesInSwitch": true,          /* Report errors for fallthrough cases in switch statement. */
+    // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
+    // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+
+    /* Module Resolution Options */
+    // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
+    // "baseUrl": "./",                             /* Base directory to resolve non-absolute module names. */
+    // "paths": {},                                 /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
+    // "rootDirs": [],                              /* List of root folders whose combined content represents the structure of the project at runtime. */
+    // "typeRoots": [],                             /* List of folders to include type definitions from. */
+    // "types": [],                                 /* Type declaration files to be included in compilation. */
+    // "allowSyntheticDefaultImports": true,        /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
+    "esModuleInterop": true,                        /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
+    // "preserveSymlinks": true,                    /* Do not resolve the real path of symlinks. */
+    // "allowUmdGlobalAccess": true,                /* Allow accessing UMD globals from modules. */
+
+    /* Source Map Options */
+    // "sourceRoot": "",                            /* Specify the location where debugger should locate TypeScript files instead of source locations. */
+    // "mapRoot": "",                               /* Specify the location where debugger should locate map files instead of generated locations. */
+    // "inlineSourceMap": true,                     /* Emit a single file with source maps instead of having a separate file. */
+    // "inlineSources": true,                       /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */
+
+    /* Experimental Options */
+    // "experimentalDecorators": true,              /* Enables experimental support for ES7 decorators. */
+    // "emitDecoratorMetadata": true,               /* Enables experimental support for emitting type metadata for decorators. */
+
+    /* Advanced Options */
+    "resolveJsonModule": true,                      /* Include modules imported with '.json' extension */
+    "skipLibCheck": true,                           /* Skip type checking of declaration files. */
+    "forceConsistentCasingInFileNames": true        /* Disallow inconsistently-cased references to the same file. */
+  }
+}

backend/nodejs/tslint.json

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+{
+    "defaultSeverity": "error",
+    "extends": [
+        "tslint:recommended"
+    ],
+    "jsRules": {},
+    "rules": {},
+    "rulesDirectory": []
+}