Add polyfills for map, filter and reduce

NachiketaDhal · NachiketaDhal · commit 57442d097e87 · 2022-10-02T11:03:49.000+05:30
diff --git a/INTERVIEW_QUESTION/mapFilterReducePolyfill.js b/INTERVIEW_QUESTION/mapFilterReducePolyfill.js
@@ -0,0 +1,33 @@
+const numbers = [1, 2, 3, 4, 5];
+
+Array.prototype.customMap = function (cb) {
+  const result = [];
+  for (let i = 0; i < this.length; i++) {
+    result.push(cb(this[i], i, this));
+  }
+  return result;
+};
+
+Array.prototype.customFilter = function (cb) {
+  const result = [];
+  for (let i = 0; i < this.length; i++) {
+    if (cb(this[i], i, this)) result.push(this[i]);
+  }
+  return result;
+};
+
+Array.prototype.customReduce = function (cb, initialValue) {
+  let prevValue = initialValue;
+  for (let i = 0; i < this.length; i++) {
+    if (prevValue) {
+      prevValue = cb(prevValue, this[i], i, this);
+    } else {
+      prevValue = this[0];
+    }
+  }
+  return prevValue;
+};
+
+console.log(numbers.customMap((number) => number * 2));
+console.log(numbers.customFilter((number) => number > 2));
+console.log(numbers.customReduce((prev, curr) => prev + curr, 0));
