Originally JavaScript didn't support `class`es, and class-like behavior had to be kludged using things like `prototype` assignments for "class" functions. Fortunately, ECMAScript 2015 added classes, so any lingering `prototype` uses should be converted to true `class`es. The new syntax is more expressive and clearer, especially to those with experience in other languages.

Specifically, with ES2015, you should simply declare a `class` and define its methods inside the class declaration.

## Noncompliant Code Example

    function MyNonClass(initializerArgs = []) {
      this._values = [...initializerArgs];
    }

    MyNonClass.prototype.doSomething = function () {  // Noncompliant
      // ...
    }

## Compliant Solution

    class MyClass {
      constructor(initializerArgs = []) {
        this._values = [...initializerArgs];
      }

      doSomething() {
        //...
      }
    }