 Simplify Passing State In React With The useContext Hook - React Hooks 101 Part 5 of 6

Day 5 of our special 6-part YouTube tutorial series on React Hooks

. Hooks are so important for all React developers to understand because, conceptually, React components have always been closer to functions and the library supports a functional way of thinking. Hooks add powerful capabilities to functional components.

Now in Tutorial 5, Paige covers a powerful Hook - the 

The use of component hierarchies solved problems in React around composing UI out of smaller individual parts, but created a range of new problems:

More importantly, passing props down became unwieldy in complex component hierarchies where the intermediate components did not need props that were intended for a component further down the hierarchy.

These problems are neatly solved for us using the Context API in React, and the 

 Hook lets you share state easily in component hierarchies without passing props down.

 Hook and how to use it in today's React Hooks tutorial.

Keep an eye out for the 6th and final tutorial in our React Hooks series. In it, we'll go in-depth into Custom Hooks and how to write your own. Mastering this skill will turn you into a much more versatile React dev.

AUTHOR

Nate Murray

React Dropdown Tutorial for Beginners: Create a Dropdown Menu from Scratch

In this hands-on tutorial, I’ll show you how to build a React dropdown menu from scratch, without any library. We’ll cover: how to get the selected value from the dropdown, and how to create the dropdown with both functional and class components.

React comes with a lot of component libraries for virtually everything you need, from forms and autocomplete search boxes to sliders and navbars. 

Although these UI libraries can speed up your work and are pretty convenient to use, they can make your project more complex and add to the bundle size. So unless you need to use a library for a specific project, it's preferable to write your own components and keep them as simple as possible. 

In this article, we'll create a basic React dropdown menu, first as a functional component, then as a class component. We won't use any library; instead, we'll define the elements of the dropdown using styled-components. 

By the end of this post, you will know how to create a basic React dropdown menu using functional and class components.

Although this is a beginner tutorial, I won't cover the basics of React, so in order to get the most out of this article you should know:

Building the React Dropdown as a Functional Component

 with React and install styled-components as a dependency. 

 file, as we won’t use it, and we’ll create a new 

 folder, where we’ll build our styled-components. 

 file where we’ll develop the component. Your project structure should look like this: 

Before we dive into the actual component, here's what we’ll cover:

To create the dropdown, we’ll use the HTML 

 element. This has the following structure: 

<select name="selectList" id="selectList">
   <option value="option 1">Option 1</option>
   <option value="option 2">Option 2</option>
</select>

So we have the dropdown element itself (the 

Next to these, we also want to display a heading on top of the dropdown, to tell the users what this list is for. So we’ll need to add a 

Finally, if we want to send the selected options to an API endpoint, we need to wrap this entire component in a 

So let’s create these components as styled-components first, in the 

file.  First, we'll create the wrapper, which is an HTML form. 

import styled from "styled-components";

export const DropdownWrapper = styled.form`
  display: flex;
  flex-flow: column;
  justify-content: flex-start;
`;

---
  
export const StyledSelect = styled.select`
  max-width: 50%;
  height: 100%;
  padding: 0.5rem;
  margin-bottom: 1rem;
`;

export const StyledOption = styled.option`
  color: ${(props) => (props.selected ? "lightgrey" : "black")};
`;

export const StyledLabel = styled.label`
  margin-bottom: 1rem;
`;

export const StyledButton = styled.input`
  max-width: 50%;
  height: 100%;
  display: flex;
  justify-content: center;
  border: solid 2px blue;
  padding: 0.5rem;
  border-radius: 1rem;
`;

Next, let's import the components and create the dropdown component skeleton in the 

import React from "react";
import {
  DropdownWrapper,
  StyledSelect,
  StyledOption,
  StyledLabel,
  StyledButton,
} from "./styles.js";

export function Dropdown(props) {
  return (
    <DropdownWrapper action={props.action}>
      <StyledLabel htmlFor="services">
        {props.formLabel}
      </StyledLabel>
      <StyledSelect id="services" name="services">
        {props.children}
      </StyledSelect>
      <StyledButton type="submit" value={props.buttonText} />
    </DropdownWrapper>
  );
}

export function Option(props) {
  return (
    <StyledOption selected={props.selected}>
      {props.value}
    </StyledOption>
  );
}

We have our dropdown component, so let's include it in the 

import React from "react";
import { Dropdown, Option } from "./Dropdown";

export default function App() {
  return (
    <div>
      <h1>Which service are you interested in?</h1>
      <Dropdown
        formLabel="Choose a service"
        buttonText="Send form"
        action="/"
      >
        <Option selected value="Click to see options" />
        <Option value="Option 1" />
        <Option value="Option 2" />
        <Option value="Option 3" />
      </Dropdown>
    </div>
  );
}

Right now, your app should look like this. 

If you select one of the options in the dropdown menu, nothing happens yet. To be able to get the value of the selected option and send it to an API endpoint, we need to add a hook. 

import React, { useState } from "react";
import { Dropdown, Option } from "./Dropdown";

export default function App() {
  const [optionValue, setOptionValue] = useState("");
  const handleSelect = (e) => {
    console.log(e.target.value);
    setOptionValue(e.target.value);
  };

  return (
    <div>
      <h1>Which service are you interested in?</h1>
      <Dropdown
        formLabel="Choose a service"
        buttonText="Send form"
        onChange={handleSelect}
        action="/"
      >
        <Option selected value="Click to see options" />
        <Option value="Option 1" />
        <Option value="Option 2" />
        <Option value="Option 3" />
      </Dropdown>
      <p>You selected {optionValue} </p>
    </div>
  );
}

Here's what we did. First, we declare a new state variable, which is called 

. We want this to be equal to the value selected from the list, so we'll add a function called 

, which will update the state variable to our selected value. 

 event handler to the Dropdown component, and to define the function that will be called. So now whenever the value of the dropdown changes, the 

 function will be called, and the state value will be updated to the one selected from the list. 

To test if this works correctly, I've added a 

tag right after the dropdown, where we'll print the state value. 

All looks good, so now the only thing that we still need to adjust is the endpoint where we send the selected value. 

I'll add a fake API endpoint, just to test if the form is submitted correctly. In the Dropdown component, add this path to the 

That's all! Now let's create the same dropdown list using a class component. 

We'll create a separate project for this, to keep things organized. You can find the code for the 

We'll reuse the same styles, so let's first add 

 file, and copy-paste the previous styles. 

 file, for our class component. Copy-paste the code from the functional component - we'll start with that and refactor as needed.

// Dropdown.js 

import React from "react";
import {
  DropdownWrapper,
  StyledSelect,
  StyledOption,
  StyledLabel,
  StyledButton,
} from "./styles.js";

export function Dropdown(props) {
  return (
    <DropdownWrapper
      action={props.action}
      onChange={props.onChange}
    >
      <StyledLabel htmlFor="services">
        {props.formLabel}
      </StyledLabel>
      <StyledSelect id="services" name="services">
        {props.children}
      </StyledSelect>
      <StyledButton type="submit" value={props.buttonText} />
    </DropdownWrapper>
  );
}

export function Option(props) {
  return (
    <StyledOption selected={props.selected}>
      {props.value}
    </StyledOption>
  );
}

// App.js

import React, { useState } from "react";
import { Dropdown, Option } from "./Dropdown";

export default function App() {
  const [optionValue, setOptionValue] = useState("");
  const handleSelect = (e) => {
    console.log(e.target.value);
    setOptionValue(e.target.value);
  };

  return (
    <div>
      <h1>Which service are you interested in?</h1>
      <Dropdown
        formLabel="Choose a service"
        buttonText="Send form"
        onChange={handleSelect}
        action="https://jsonplaceholder.typicode.com/posts"
      >
        <Option selected value="Click to see options" />
        <Option value="Option 1" />
        <Option value="Option 2" />
        <Option value="Option 3" />
      </Dropdown>
      <p>You selected {optionValue} </p>
    </div>
  );
}

 hook as we won't use it. Instead, we'll initiate the state in a constructor, as follows: 

// App.js

class App extends React.Component {
  constructor(props) {
    super(props);
    this.state = { value: "" };
  }
}

 to the component, to output our dropdown menu.

 render() {
    return (
      <div>
        <h1>Which service are you interested in?</h1>
        <Dropdown
          formLabel="Choose a service"
          buttonText="Send form"
	      onChange={this.handleSelect}          
          action="/"
        >
          <Option selected value="Click to see options"/>
          <Option value="Option 1" />
          <Option value="Option 2" />
          <Option value="Option 3" />
        </Dropdown>
        <p>You selected {this.state.value} </p>
      </div>
    );
  }

The rest of the component is the same as before, but we've added 

 handler as well as to the selected value. 

 function as well, and to add it to the constructor. 

import React from "react";
import { Dropdown, Option } from "./Dropdown";

class App extends React.Component {
  constructor(props) {
    super(props);
    this.state = { value: "" };

    this.handleSelect = this.handleSelect.bind(this);
    this.handleSubmit = this.handleSubmit.bind(this);
  }

  handleSelect(event) {
    this.setState({ value: event.target.value });
  }

  handleSubmit(event) {
    event.preventDefault();
    console.log(this.state.value);
  }

  render() {
    return (
      <div>
        <h1>Which service are you interested in?</h1>
        <Dropdown
          formLabel="Choose a service"
          buttonText="Send form"
          onChange={this.handleSelect}          action="https://jsonplaceholder.typicode.com/posts"
        >
          <Option value="Click to see options" />
          <Option value="Option 1" />
          <Option value="Option 2" />
          <Option value="Option 3" />
        </Dropdown>
        <p>You selected {this.state.value} </p>
      </div>
    );
  }
}

export default App;

 at the end, so now if we reload the app, we should see exactly the same form as before: 

As you can see, creating your own React dropdown menu, selecting a value from the list, and sending it to a backend API endpoint is pretty straight-forward, regardless of which type of component you choose: functional or class component.

If you'd like to learn more, check out these React tutorials: 

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Amelia Wattenberger

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Simplify Passing State In React With The useContext Hook - React Hooks 101 Part 5 of 6

React Dropdown Tutorial for Beginners: Create a Dropdown Menu from Scratch

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