Create polyfills.js

Author: ps0305

Coding Interview Prep/polyfills.js

@@ -0,0 +1,37 @@
+// map
+
+Array.prototype.ourMap = function(callback) {
+  var arr = [] // since, we need to return an array
+  for (var i = 0; i < this.length; i++) {
+    arr.push(callback(this[i], i, this)) // pushing currentValue, index, array
+  }
+  return arr // finally returning the array
+}
+
+
+// filter
+
+Array.prototype.filterAlbums = function(callback, context) {
+  arr = []
+  for (var i = 0; i < this.length; i++) {
+    if (callback.call(context, this[i], i, this)) {
+      arr.push(this[i])
+    }
+  }
+  return arr
+}
+
+// reduce
+
+Array.prototype.reduceAlbums = function(callback, initialValue) {
+  var accumulator = initialValue === undefined ? undefined : initialValue
+
+  for (var i = 0; i < this.length; i++) {
+    if (accumulator !== undefined) {
+      accumulator = callback.call(undefined, accumulator, this[i], i, this)
+    } else {
+      accumulator = this[i]
+    }
+  }
+  return accumulator
+} // our polyfill for reduce