add iterator design pattern

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

Author: nimit95

Behavioral/iterator.js

@@ -0,0 +1,41 @@
+const fs = require('fs');
+
+class Iterator {
+ getNext() {}
+ hasNext() {}
+}
+
+// Internally maintains list of files in the folder
+class FileBufferIterator extends Iterator {
+ constructor(folderPath) {
+ super();
+ this.folderPath = folderPath;
+ this.currentPosition = 0;
+ this.init();
+ }
+ init() {
+ const folderPath = this.folderPath;
+ let fileList = fs.readdirSync(folderPath);
+ console.log(fileList);
+ fileList = fileList.map(fileName => folderPath + "/" + fileName);
+ this.fileBuffer = fileList.map(filePath => fs.readFileSync(filePath));
+ }
+ getNext() {
+ if(this.hasNext()) {
+ return this.fileBuffer[this.currentPosition++];
+ }
+ }
+ hasNext() {
+ return this.fileBuffer.length > this.currentPosition;
+ }
+}
+
+function totalSize(iterator) {
+ let size = 0;
+ while(iterator.hasNext()) {
+ size += iterator.getNext().length;
+ }
+ return size;
+}
+
+console.log(totalSize(new FileBufferIterator(__dirname)));

Structural/composite.js

@@ -1,8 +1,6 @@
 
 class ContentBuffer {
- getSize() {
- return this.buf.length || 0;
- }
+ getSize() { }
 }
 
 // Composite Class has children as filebuffer
@@ -24,6 +22,9 @@ class FileBuffer extends ContentBuffer {
  this.buf = buf;
  return this;
  }
+ getSize() {
+ return this.buf.length || 0;
+ }
 }
 
 const file1 = new FileBuffer().setBuffer(Buffer.from("hello"));

buildDocs.js

@@ -32,6 +32,7 @@ const sections = [
  topics: [
  { name: 'chainOfResponsibility', path: './Behavioral' },
  { name: 'command', path: './Behavioral' },
+ { name: 'iterator', path: './Behavioral' },
  ]
  }
 ];

docs.md

@@ -19,6 +19,7 @@
 **[ Behavioral](#behavioral)**
 * [Chain Of Responsibility](#chain-of-responsibility)
 * [Command](#command)
+* [Iterator](#iterator)
 
 
 
@@ -408,9 +409,7 @@ new Post("jsonplaceholder.typicode.com/posts/1", ApiRequestFactory.createApiRequ
 ```Javascript
 
 class ContentBuffer {
- getSize() {
- return this.buf.length || 0;
- }
+ getSize() { }
 }
 
 // Composite Class has children as filebuffer
@@ -432,6 +431,9 @@ class FileBuffer extends ContentBuffer {
  this.buf = buf;
  return this;
  }
+ getSize() {
+ return this.buf.length || 0;
+ }
 }
 
 const file1 = new FileBuffer().setBuffer(Buffer.from("hello"));
@@ -732,5 +734,51 @@ exampleStream.on('disconnect', new DisconnectCallback());
 exampleStream.connect();
 ```
 
+### Iterator
+##### iterator.js
+```Javascript
+const fs = require('fs');
+
+class Iterator {
+ getNext() {}
+ hasNext() {}
+}
+
+// Internally maintains list of files in the folder
+class FileBufferIterator extends Iterator {
+ constructor(folderPath) {
+ super();
+ this.folderPath = folderPath;
+ this.currentPosition = 0;
+ this.init();
+ }
+ init() {
+ const folderPath = this.folderPath;
+ let fileList = fs.readdirSync(folderPath);
+ console.log(fileList);
+ fileList = fileList.map(fileName => folderPath + "/" + fileName);
+ this.fileBuffer = fileList.map(filePath => fs.readFileSync(filePath));
+ }
+ getNext() {
+ if(this.hasNext()) {
+ return this.fileBuffer[this.currentPosition++];
+ }
+ }
+ hasNext() {
+ return this.fileBuffer.length > this.currentPosition;
+ }
+}
+
+function totalSize(iterator) {
+ let size = 0;
+ while(iterator.hasNext()) {
+ size += iterator.getNext().length;
+ }
+ return size;
+}
+
+console.log(totalSize(new FileBufferIterator(__dirname)));
+```
+