Add JavaScript examples

Author: tshemsedinov

JavaScript/1-callback.js

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+'use strict';
+
+// Callback passing
+
+class Server {
+  shutdown(callback) {
+    console.log('Shutting down...');
+    callback();
+  }
+}
+
+// Usage
+
+const server = new Server();
+server.shutdown(() => {
+  console.log('Bye!');
+  process.exit(0);
+});

JavaScript/2-revealing.js

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+'use strict';
+
+// Revealing constructor
+
+class Server {
+  constructor(log) {
+    this.log = log;
+  }
+
+  shutdown() {
+    this.log('Shutting down...');
+  }
+}
+
+// Usage
+
+const server = new Server(console.log);
+server.shutdown();
+console.log('Bye!');

JavaScript/3-injection.js

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+'use strict';
+
+// Dependency injection
+
+class Server {
+  constructor(logger) {
+    this.logger = logger;
+  }
+
+  shutdown() {
+    this.logger.log('Shutting down...');
+  }
+}
+
+// Usage
+
+const server = new Server(console);
+server.shutdown();
+console.log('Bye!');

JavaScript/4-module.js

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+'use strict';
+
+// Service locator: require or import
+
+const { Logger } = require('./logger.js');
+
+class Server {
+  constructor() {
+    this.logger = new Logger();
+  }
+
+  shutdown() {
+    this.logger.log('Shutting down...');
+  }
+}
+
+// Usage
+
+const server = new Server();
+server.shutdown();
+console.log('Bye!');

JavaScript/5-locator.js

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+'use strict';
+
+// Service locator
+
+const { ServiceLocator } = require('./locator.js');
+
+class Server {
+  constructor() {
+    const { Logger } = ServiceLocator.get('logger');
+    this.logger = new Logger();
+  }
+
+  shutdown() {
+    this.logger.log('Shutting down...');
+  }
+}
+
+// Usage
+
+const server = new Server();
+server.shutdown();
+console.log('Bye!');

JavaScript/6-subst.js

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+'use strict';
+
+// Service locator
+
+const { ServiceLocator } = require('./locator.js');
+
+class Server {
+  constructor() {
+    const { Logger } = ServiceLocator.get('logger');
+    this.logger = new Logger();
+  }
+
+  shutdown() {
+    this.logger.log('Shutting down...');
+  }
+}
+
+// Usage
+
+class Logger {
+  constructor() {
+    return console;
+  }
+}
+
+ServiceLocator.set('logger', { Logger });
+const server = new Server();
+server.shutdown();
+console.log('Bye!');

JavaScript/7-closure.js

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+'use strict';
+
+// Closure: class factory
+
+const createServerClass = (dependencies) => {
+  class Server {
+    constructor() {
+      const { Logger } = dependencies;
+      this.logger = new Logger();
+    }
+
+    shutdown() {
+      this.logger.log('Shutting down...');
+    }
+  }
+
+  return Server;
+};
+
+// Usage
+
+class Logger {
+  constructor() {
+    return console;
+  }
+}
+
+const Server = createServerClass({ Logger });
+const server = new Server();
+server.shutdown();
+console.log('Bye!');

JavaScript/locator.js

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+'use strict';
+
+class ServiceLocator {
+  static #modules = new Map();
+
+  static get(moduleName) {
+    return ServiceLocator.#modules.get(moduleName);
+  }
+
+  static set(moduleName, exp) {
+    ServiceLocator.#modules.set(moduleName, exp);
+  }
+}
+
+const logger = require('./logger.js');
+ServiceLocator.set('logger', logger);
+
+module.exports = { ServiceLocator };
+
+// Alternative implementations:
+// https://github.com/HowProgrammingWorks/ServiceLocator

JavaScript/logger.js

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+'use strict';
+
+class Logger {
+  log(message) {
+    process.stdout.write(message + '\n');
+  }
+}
+
+module.exports = { Logger };