add stream code

Author: wangding

09-stream/06-my-readable.js

@@ -2,20 +2,18 @@
 
 const { Readable } = require('stream');
 
-let c = 'a'.charCodeAt(0);
-
 class MyReadable extends Readable {
   constructor() {
     super();
   }
 
   _read() {
-    this.push(String.fromCharCode(c++));
-    if (c>'z'.charCodeAt(0)) {
-      this.push(null);
-    }
+    this.push(String.fromCharCode(this.#c++));
+    if (this.#c>'z'.charCodeAt(0)) this.push(null);
   }
+
+  #c = 'a'.charCodeAt(0);
 }
 
-let rs = new MyReadable();
+const rs = new MyReadable();
 rs.pipe(process.stdout);

09-stream/10-rgb.js

@@ -0,0 +1,25 @@
+#!/usr/bin/env node
+
+const { Readable } = require('stream');
+
+class RGB extends Readable {
+  constructor(num) {
+    super();
+    this.#num = num;
+  }
+
+  _read() {
+    this.#pos++ > this.#num ? this.push(null) : this.push(this.#rgb());
+  }
+
+  #rgb() {
+    let x = Math.round(Math.random()*100);
+    return x <= 60 ? 'R' : ( x <= 75 ? 'G':'B');
+  }
+
+  #num = 0;
+  #pos = 0;
+}
+
+const rs = new RGB(100);
+rs.pipe(process.stdout);