feat: added polyfill for setTimeout solution in INTERVIEW_QUESTIONS

imanshu03 · imanshu03 · commit c3f1253f8d0c · 2022-10-02T14:24:02.000+05:30
diff --git a/INTERVIEW_QUESTION/Polyfills/setTimeout.js b/INTERVIEW_QUESTION/Polyfills/setTimeout.js
@@ -0,0 +1,73 @@
+// NOTE: Run this script in browser snippets as running on Node.js environment will throw `window is not defined` error.
+
+
+(function () {
+    // Object to store registered timers
+    const timerCallbackMap = {};
+  
+  
+    // Function to generate unique ids for a particular callback
+    function generateId() {
+      const chars = "12356ABCDEF";
+      let key = "";
+      for (let i = 0; i < 6; i++) {
+        const idx = Math.floor(Math.random() * chars.length);
+        key += chars[idx];
+      }
+      return key;
+    }
+  
+  
+    // Function to be called when browser is idle to check if any callback execution time is pass the current time
+    function check() {
+      if (timerCallbackMap.size === 0) return;
+  
+      for (let timerId in timerCallbackMap) {
+        const now = Date.now();
+        if (now > timerCallbackMap[timerId].execTime) {
+          timerCallbackMap[timerId].callback();
+          window.myClearTimeout(timerId);
+        }
+      }
+  
+      requestIdleCallback(check);
+    }
+  
+  
+    // Polyfill for setTimeout
+    window.mySetTimeout = function (callback, delay = 0) {
+      // check if arguments are of correct type
+      if (typeof callback !== "function") throw new Error("cb should be a function");
+      if (typeof delay !== "number" || delay < 0)
+        throw new Error("delay should be a positive number");
+  
+      
+      // generate unique id for callback
+      const timerId = generateId();
+  
+  
+      // store the callback and set its execution time as current epoch value + delay in milliseconds
+      timerCallbackMap[timerId] = {
+        callback,
+        execTime: Date.now() + delay
+      };
+  
+      // queue the check function to be called when browser is idle
+      if (Object.keys(timerCallbackMap).length === 1) requestIdleCallback(check);
+  
+      return timerId;
+    };
+  
+  
+    // Polyfill for clearTimeout
+    window.myClearTimeout = function (timerId) {
+      if (timerCallbackMap[timerId]) {
+        delete timerCallbackMap[id];
+      }
+    };
+  })();
+  
+  const id = mySetTimeout(() => {
+    console.log("Hello");
+  }, 2000);
+  
