How do I define methods in stateless components?

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If I simply have:

const App = function() {
    return (
        <div>{this.renderList()}</div>
    )

}

How do I define the renderList method?

I can't do const renderList = function() {} (nor with var or let). I can't do renderList() {}.

What's the right syntax?

I am hesitant to give a solution to this because inline Stateless Functions are not supposed to have methods. if you want a method you should use a Class and theres nothing wrong with using a class. Its all based on what you need to do. Stateless Functions are designed to be a super light weight way to render something that doesn't need methods, or a state or even a this context (in terms of a class).

you should be doing it like this.

class App extends Component {
    constructor(){
        super();
        // note this is a Stateless Component because its a react class without a state defined.
    }
    renderList = () => {
        return <span>Something Here</span>;
    }
    render() {
        return <div>{this.renderList()}</div>
    }
}

a HACK way that I wouldn't recommend (but does solve your question in the way you want it to) would be like this.

const App = () => {
    let renderList = () => {
        return <span>Something Here</span>
    }
    return <div>{renderList()}</div>
}

The reason why its generally a bad practice is because you are creating a function and all the memory allocation needed every render cycle. Subsequently, the internal diffing optimizations that react provides is generally useless if you do this because a new function gives a different signature than the prior render cycle. If this had a lot of children, they would all be forced to re-render!

Edit - React Version 16.8.0 +

You can use Hooks to do this. I would recommend using memo to memoize the function, this way you aren't creating it in memory each render cycle.

const RenderList = React.memo(props => (
  <span>Something Here</span>
))

React Function Components, We can convert this entire class into a functional React component using Now we'll define a componentDidMount() method to update the  Stateless components are components that don’t hold state. We can define stateless components with function and class components. They only take props and render them.

const App = function() {
  const renderList = ()=> {
      return "this variables"
     }

    return (
        <div>{renderList()}</div>
    )

}

Five Ways to Convert React Class Components to Functional , This problem is basically not related to React component but more “how do you define your arguments in functions”. I will stick to React but this argument can be​  The goals of this article are to define what stateful and stateless components are, otherwise known as smart and dumb - or container and presentational components. For the purposes of the article, we’ll be using Angular 2 Components to explain the stateful/stateless concepts.

Can you try something like

const App = () => {
  return (
    <div>{this.renderList()}</div>
  )
}

App.renderList = () => {
    return 'This is my list'
}

How I write React stateless functional components, Next, define our Component as a Function rather than Class Component. Constructor and initial state. Instead of defining initial state in a  It is great for allowing you to define complex stateful components that define large parts of our app logic. For doing all of that, you need the full power classes provide. You want to extend the Component base class to have access to the state API, lifecycle methods, and other React features.

You would want to do something like this

const App = function() {

    return (
        <div>{renderList()}</div>
    )

}
  function renderList(){
      return "this variables"
     }

Naturally this is a bad approach you its recommended that you pass in functions as props and stateless component are always dumb componets. Say if you are using redux for example you can have your component render like this

import {connect} from 'react-redux';
const App = (props) => {
   return (
      <div> {props.renderList} </div>
    )
}
function renderList (){
   return "your render logic"
}
export default connect(null, {renderList})(App)

Add state and lifecycle methods to Function Components with React , Getting Back to Functions. The syntax we have been using so far for defining components has looked as follows: class LightningCounter extends React. Function components (formerly ‘Stateless’ components) To delve into each component type, we’ll use TypeScript type definitions. This aids in seeing which features are available from a high-level. No prior knowledge of TypeScript is necessary. We’ll look at what the type definition means and how it’s useful to us.

You can create render list function as standalone and use function parameter to pass props into function.

Stateless Functional Components, Since functional components offer no state or lifecycle methods, you to continuously log the state of the component to understand what is  For all these reasons, we should strive to use stateless functional components wherever possible. Stateless components are just the latest reason why I love teaching React. React stateless functions offer the most elegant approach I’ve seen for creating a reusable component in any popular framework. Yes, even including Angular 2.

React Functional or Class Components: Everything you need to know, setState , we use it to set the state(s) of our functional component. const [state, setState] = useState(initialState). useState returns a value and a  STATELESS COMPONENT declared as a function that has no state and returns the same markup given the same props. A quote from the React documentation: These components must not retain internal state,

React Hooks: A transition of functions from stateless to stateful , There are definitely times I'll write a stateless class component so I can define callback methods as class properties (especially if I'm passing  In React, stateless components are not necessarily pure components according to the definition above if you call "stateless" a component that never calls this.setState and that doesn't use this.state. In fact, in a PureComponent, you can still perform side-effects during lifecycle methods.

Functional Stateless Components in React, Since React v14, a simpler way was introduced to define stateless functional components. These components use plain Javascript functions. Adding Lifecycle Methods to a Class . In applications with many components, it’s very important to free up resources taken by the components when they are destroyed. We want to set up a timer whenever the Clock is rendered to the DOM for the first time. This is called “mounting” in React.

Comments
  • what do you want renderList to do?
  • @JohnRuddell Render a list.
  • I get that. I mean what kind of list? like whats rendering this component? what are the contents of renderList?
  • @JohnRuddell dropping in from 2018, you are so patient to deal with this guy in the chat!
  • Fun to come back to in 2019 as React has moved from stateless, pure functions not having state or methods etc to it almost being the preferred way to create components: 2016: "Dont put methods in your function, u idiot! They're supposed to be pure! Its v. simple. Classes for logic / state. Functions for pure, dumb rendering, no state, no lifecycles 2019: "Hey, use useState & useEffect to manage lifecycle & state & by all means create methods but u cant access them outside like a class, so think carefully re what actually needs to be in your component & what should live in utils
  • The docs literally call them stateless functions. from the docs.. says they are pure functions of their props and that they must not retain internal state, do not have backing instances, and do not have the component lifecycle methods. theres no lifecycle methods. theres no backing instances aka this.someMethod its right there in the docs man
  • its a function. its not a class. functions dont have methods classes do. its a basic javascript thing. in es5 it would be prototype methods but not the function
  • @JohnRuddell I applaud your patience
  • @ivarni haha thanks man. just trying to help him understand. I was where he was once (but maybe not as aggressive.. and rude.. and unwilling to listen). anyways. Yeats forget stateless functions/components or whatever you want to call it for a minute. just think about basic vanilla javascript. create a function and look at what this is. create a class and look at what this is
  • Hey @ebr I am on the road so I may be brief but yes, the reason why it is a bad idea is because you are creating a function and all the memory allocation needed every render cycle. Subsequently, the internal diffing optimizations that react provides is generally useless if you do this because a new function gives a different signature than the prior render cycle. If you don't need state, then define that function as a standalone (not inside your component function) and pass props.. basically another functional component. That way the function is created once at runtime. Hope that helps!