add strategy design patttern

Signed-off-by: Nimit <nimitagg95@gmail.com>

Author: nimit95

Behavioral/lib.js

@@ -0,0 +1,60 @@
+const net = require('net');
+const http = require('http');
+
+// Abstract Product Class
+class ApiRequest {
+ makeGetRequest(url) {
+ return Error(`Implement make Get Request for ${url}`);
+ }
+}
+
+// Product A
+class tcpApiRequest extends ApiRequest {
+ makeGetRequest(url) {
+ // Handling simple get request without query params
+ return new Promise((resolve, reject) => {
+ const socket = net.createConnection({
+ host: "www.example.com",
+ port: "80"
+ });
+
+ socket.on('data', (data) => resolve(data.toString()));
+
+ socket.on('error', err => reject(err));
+ 
+ socket.end(`GET / HTTP/1.1\r\nHost: ${url}\r\n\r\n`);
+ });
+ 
+ }
+}
+
+// Product B
+class httpApiRequest extends ApiRequest {
+ makeGetRequest(url) {
+ // Handling simple get request without query params
+ return new Promise((resolve, reject) => {
+ http.request(`http://${url}`, (res) => {
+ res.on('data', data => resolve(data.toString()));
+ res.on('error', err => reject(err));
+ }).end();
+ });
+ }
+}
+
+/**
+ * This is an abstract factory interface. Uses a static function to 
+ * generate family of products.
+ */
+class ApiRequestFactory {
+ static createApiRequest(kind) {
+ // This can easily be extended to include HTTPS, HTTP2, HTTP3
+ switch(kind) {
+ case "tcp":
+ return new tcpApiRequest();
+ case "http":
+ return new httpApiRequest();
+ }
+ }
+}
+
+module.exports = ApiRequestFactory;

Behavioral/strategy.js

@@ -0,0 +1,36 @@
+/**
+ * ApiRequestFactory gives underlying startegies for Ali request
+ */
+const ApiRequestFactory = require("./lib");
+class UpstreamFile {
+ getFileUpstream() { }
+}
+/**
+ * Here by default Stategy for API request is http
+ */
+class Config extends UpstreamFile {
+ constructor(url, apiRequest) {
+ super();
+ this.url = url;
+ this.apiRequest = apiRequest || ApiRequestFactory.createApiRequest("http");
+ }
+ getFileUpstream() {
+ this.apiRequest
+ .makeGetRequest(this.url)
+ .then(response => console.log(response))
+ .catch(err => console.log(err));
+ }
+}
+
+/**
+ * AbstractFactory is used to generate related implementation for these 
+ * classes
+ */
+const config = new Config("jsonplaceholder.typicode.com/posts/1");
+// Using default config http
+config.getFileUpstream();
+
+const config2 = new Config("https://jsonplaceholder.typicode.com/todos/1",
+ ApiRequestFactory.createApiRequest("tcp"));
+// Get tcp strategy
+config2.getFileUpstream();

buildDocs.js

@@ -37,6 +37,7 @@ const sections = [
  { name: 'memento', path: './Behavioral' },
  { name: 'observer', path: './Behavioral' },
  { name: 'state', path: './Behavioral' },
+ { name: 'strategy', path: './Behavioral' },
  ]
  }
 ];

docs.md

@@ -24,6 +24,7 @@
 * [Memento](#memento)
 * [Observer](#observer)
 * [State](#state)
+* [Strategy](#strategy)
 
 
 
@@ -1021,5 +1022,47 @@ socket.printState();
 setTimeout(() => socket.printState(), 1000);
 ```
 
+### Strategy
+##### strategy.js
+```Javascript
+/**
+ * ApiRequestFactory gives underlying startegies for Ali request
+ */
+const ApiRequestFactory = require("./lib");
+class UpstreamFile {
+ getFileUpstream() { }
+}
+/**
+ * Here by default Stategy for API request is http
+ */
+class Config extends UpstreamFile {
+ constructor(url, apiRequest) {
+ super();
+ this.url = url;
+ this.apiRequest = apiRequest || ApiRequestFactory.createApiRequest("http");
+ }
+ getFileUpstream() {
+ this.apiRequest
+ .makeGetRequest(this.url)
+ .then(response => console.log(response))
+ .catch(err => console.log(err));
+ }
+}
+
+/**
+ * AbstractFactory is used to generate related implementation for these 
+ * classes
+ */
+const config = new Config("jsonplaceholder.typicode.com/posts/1");
+// Using default config http
+config.getFileUpstream();
+
+const config2 = new Config("https://jsonplaceholder.typicode.com/todos/1",
+ ApiRequestFactory.createApiRequest("tcp"));
+// Get tcp strategy
+config2.getFileUpstream();
+
+```
+