mfdeveloper · January 6, 2018 16:16 · Jan 6, 2018
diff --git a/instance-loader.ts b/instance-loader.ts
@@ -0,0 +1,41 @@
+/**
+ * Creates a dynamic instance of a specific class/prototype.
+ * Minor changes from initial solution shared by **Steve Fenton**
+ * 
+ * WARNING: This solution don't works on Angular applications,
+ * using JIT (because the webpack don't compiles classes into window object)
+ * or AOT (js minification for production build) compilation.
+ * 
+ * @see https://www.stevefenton.co.uk/2014/07/creating-typescript-classes-dynamically/
+ */
+export class InstanceLoader {
+
+  static getInstance<T>(context: { [key: string]: any }, name: string, ...args: any[]): T {
+    const classRef: { new (...args: any[]): any; } = context[name];
+
+    if (!classRef) {
+      throw new Error(`The class '${name}' was not found`);
+    }
+
+    let instance = Object.create(classRef.prototype);
+
+    try {
+      instance.constructor.apply(instance, args);
+    } catch (err) {
+      /**
+       * For ES2015(ES6): constructor.apply is not allowed
+       */
+      if (/Class constructor/.test(err.toString())) {
+        instance = class extends classRef {
+          constructor(...params: any[]) {
+            super(...params);
+          }
+        };
+
+        return <T>new instance(args);
+      }
+    }
+
+    return <T>instance;
+  }
+}