What happens if I don't use this when referencing a method from inside a class?

Question

What happens if I don’t use this when referencing a method from inside a class?

Answer

When calling or referencing a method that’s defined on a class from inside another method on the same class, we need to use this to tell our method where to find the method we’re trying to call/reference. If we do not use this, our method will look for the method name (we’re referencing/calling) within the scope of it’s own definition and won’t be able to find it!

For example:

import React from 'react';
import ReactDOM from 'react-dom';

class NounGreeting extends React.Component {
  noun() {
    return 'Dog';
  }

  render() {
    return <h1>Hello {this.noun()}.</h1>; //here `this` is refrring to the `noun` method defined on our `NounGreeting` class
  }
}

ReactDOM.render(<NounGreeting />, document.getElementById('app'));

vs.:

import React from 'react';
import ReactDOM from 'react-dom';

class NounGreeting extends React.Component {
  noun() {
    return 'Dog';
  }

  render() {
    return <h1>Hello {noun()}.</h1>; //here we would run into an error `'noun' is not defined` - this is because our `render` method is looking inside the scope of it's own definition for the `noun` method
  }
}

ReactDOM.render(<NounGreeting />, document.getElementById('app'));
10 Likes

didn’t the lesson teach that we don’t use () on get method calls within the class component?

12 Likes

lol. True that. The answer does not use “get” in front of method definition either.

4 Likes

This is the first time I’ve understood what the this keyword is doing, thanks for the clear explanation.

Would be interested to know why you’ve not used the get method in your example though?

4 Likes

It’s not a typo, she called a method not a get method.

5 Likes

I understand. The course teaches to use get method for something like this and the q&a does not use the get method, hence confusing within the context.

1 Like

I don’t really think that the course stipulates the use of the ‘get’ keyword.

In fact, I really appreciate the fact that she omitted the get in her example, a silent reminder that we do not use parens with getter functions, and we use them when they are not so.

8 Likes

10-4. And in full agreement with that statement.

So then why sometimes you use get (as in the lesson) and sometimes you don’t (here)?

2 Likes

getter method is used to get a property value of that class setter method is almost same but changes it

It depends on what you want to do, you don’t have to use getters but if you want you can.
You should learn as many tools as you can, so when you need to do something you can easily find the right tool.

1 Like

why you use this.noun() instead of this.noun ?
if reason is ‘get’ then why do we not use () with onclick?

1 Like

If you use onClick={function()}, it will immediately call the function upon rendering. You want to pass the function, not call it, so that it only calls when the click event happens.