Update B-class-components.md

lessons/05-react-capabilities/B-class-components.md

@@ -55,7 +55,7 @@ export default WrappedDetails;
 
 - Every class component extends `React.Component`. Every class component must have a render method that returns some sort of JSX / markup / call to `React.createElement`.
 - Not every component needs to have a constructor. Many don't. I'll show you momentarily how you nearly never need to have one. In this case we need it to instantiate the state object (which we'll use instead of `useState`.) If you have a constructor, you _have_ to do the `super(props)` to make sure that the props are passed up to React so React can keep track of them.
-- `componentDidMount` is a function that's called after the first rendering is completed. This pretty similar to a `useEffect` call that only calls the first time. This is typically where you want to do data fetching. It doesn't have to be async; we just made it async here to make the data fetching easy.
+- `componentDidMount` is a function that's called after the first rendering is completed. This is pretty similar to a `useEffect` call that only calls the first time. This is typically where you want to do data fetching. It doesn't have to be async; we just made it async here to make the data fetching easy.
 - Notice instead of getting props via parameters and state via `useState` we're getting it from the instance variables `this.state` and `this.props`. This is how it works with class components. Neither one will you mutate directly.
   - `this.state` is the mutable state of the component (like useState). You'll use `this.setState` to mutate it (don't modify it directly.)
   - `this.props` comes from the parent component, similar to parameter given to the render functions that we pull props out of.