HowProgrammingWorks
diff --git a/‎JavaScript/5-operators.js
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+60Lines changed: 60 additions & 0 deletions b/‎JavaScript/5-operators.js
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+60Lines changed: 60 additions & 0 deletions
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+'use strict';
+
+class Observable {
+  constructor() {
+    this.observers = [];
+    this.operators = [];
+  }
+  subscribe(observer) {
+    this.observers.push(observer);
+    return this;
+  }
+  notify(data) {
+    if (this.observers.length === 0) return;
+    for (const operator of this.operators) {
+      if (operator.name === 'filter') {
+        if (!operator.fn(data)) return;
+      }
+      if (operator.name === 'map') {
+        data = operator.fn(data);
+      }
+    }
+    for (const observer of this.observers) {
+      observer(data);
+    }
+  }
+  filter(predicate) {
+    this.operators.push({ name: 'filter', fn: predicate });
+    return this;
+  }
+  map(callback) {
+    this.operators.push({ name: 'map', fn: callback });
+    return this;
+  }
+}
+
+// Usage
+
+const randomChar = () => String
+  .fromCharCode(Math.floor((Math.random() * 25) + 97));
+
+let count = 0;
+
+const observable = new Observable()
+  .filter(char => !'aeiou'.includes(char))
+  .map(char => char.toUpperCase())
+  .subscribe(observer);
+
+const timer = setInterval(() => {
+  const char = randomChar();
+  observable.notify(char);
+}, 200);
+
+function observer(char) {
+  process.stdout.write(char);
+  count++;
+  if (count > 50) {
+    clearInterval(timer);
+    process.stdout.write('\n');
+  }
+}