Question 74340 in Reactjs Question posted in
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Button component doesn't work with useContext hook – Reactjs

I am practicing useContext hook with Next.js if it matters and created a small site that changes background color of <Paragraph></Paragraph> element for printing text and <Button></Button> element to change theme. I organized it with <Layout /> where button and paragraph are placed.

As written in tutorial, I can place this theme change logic into onClick method and it will work. It actually works, but only if I put a simple <button></button> element, but not react component:

<ThemeContext.Provider value={theme}>
                  <Paragraph>Hello Context</Paragraph>
 // Doesn't work ---> <Button type="button" onClick={() => {theme === 'dark' ? setTheme('light') : setTheme('dark')}}>Change theme</Button>
 // Works        ---> <button type="button" onClick={() => {theme === 'dark' ? setTheme('light') : setTheme('dark')}}>Change theme</button>
            </ThemeContext.Provider>

Paragraph.tsx:

import { useContext, useState, ReactNode, DetailedHTMLProps, HTMLAttributes } from 'react';
import styles from './Paragraph.module.scss'
import cn from 'classnames'
import { ThemeContext } from '../../Layout/Layout'

interface ParagraphProps extends DetailedHTMLProps<HTMLAttributes<HTMLParagraphElement>, HTMLParagraphElement> {  
      children: ReactNode
}

export const Paragraph = ({ children, className }: ParagraphProps): JSX.Element => {
      const theme = useContext<string>(ThemeContext)

      return (
            <p className={cn(styles.p, className, {
                  [styles.paraDark]: theme === 'dark',
                  [styles.paraLight]: theme === 'light'
            })}>
                  {children}
            </p>
      )
}

Button.tsx:

import { DetailedHTMLProps, ButtonHTMLAttributes, ReactNode, useContext, useState, MouseEventHandler } from 'react';
import { ThemeContext } from 'Layout/Layout';
import cn from 'classnames'
import styles from './Button.module.scss'

interface ButtonProps extends DetailedHTMLProps<ButtonHTMLAttributes<HTMLButtonElement>, HTMLButtonElement> {
      children: ReactNode
}
 
export const Button = ({ children, className}: ButtonProps ): JSX.Element => {
      const theme = useContext<string>(ThemeContext)

      return (
            <button
                  className={cn(styles.button, className, {
                        [styles.buttonDark]: theme === 'dark',
                        [styles.buttonLight]: theme === 'light'
                  })}
            >
                  {children}
            </button>
      )
}

Layout.tsx:

import { Paragraph, Button } from "Components";
import { createContext, useState } from 'react';

interface Layout {}

export const ThemeContext = createContext<string>('')

export const Layout = (): JSX.Element => {
      const [theme, setTheme] = useState<string>('dark')

      // Putting this function into onClick event also doesn't help
      const handleChangeThemeButtonClick = () => {
            if (theme === 'dark')
                  setTheme('light')
            else if (theme === 'light')
                  setTheme('dark')
      }

      return (
            <ThemeContext.Provider value={theme}>
                  <Paragraph>Hello Context</Paragraph>
                  <Button type="button" onClick={() => {theme === 'dark' ? setTheme('light') : setTheme('dark')}}>Change theme</Button>
                  <button type="button" onClick={() => {theme === 'dark' ? setTheme('light') : setTheme('dark')}}>Change theme</button>
            </ThemeContext.Provider>
      )
}

I was learing this hook on react beta docs and my code looks identical to what’s written in this tutorial.

Tags:

2

Answers


  1. 0

    It seems like you haven’t added an onClick handler to the Button component. You can add an onClick event listener to the button element inside the Button component like this:

    import { DetailedHTMLProps, ButtonHTMLAttributes, ReactNode } from 'react';

interface ButtonProps extends DetailedHTMLProps<ButtonHTMLAttributes<HTMLButtonElement>, HTMLButtonElement> {
  children: ReactNode;
  className?: string;
  onClick?: () => void;
}

export const Button = ({ children, className, onClick }: ButtonProps): JSX.Element => {
  return (
    <button className={className} onClick={onClick}>
      {children}
    </button>
  );
};

    Dont forget the props which handles onClick, i would suggest to call it something else eg "onPress" not to confuse with native onClick event.

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  2. 0

    Your Button component doesn’t have an onClick property.

    You need to pass it down as a prop and call it from the native button onClick property.

    Since you’re using typescript, give it the appropriate type of MouseEventHandler<HTMLButtonElement>, and mark it as optional (with ? after the property name in the type declaration) in case you want to use Button without an onClick event.

    import { DetailedHTMLProps, ButtonHTMLAttributes, ReactNode, useContext, useState, MouseEventHandler } from 'react';
import { ThemeContext } from 'Layout/Layout';
import cn from 'classnames'
import styles from './Button.module.scss'

interface ButtonProps extends DetailedHTMLProps<ButtonHTMLAttributes<HTMLButtonElement>, HTMLButtonElement> {
      children: ReactNode
      onClick?: MouseEventHandler<HTMLButtonElement> // <= pass it down as a prop with the appropriate type
}
 
export const Button = ({ children, className, onClick }: ButtonProps ): JSX.Element => {
      const theme = useContext<string>(ThemeContext)

      return (
            <button
                  className={cn(styles.button, className, {
                        [styles.buttonDark]: theme === 'dark',
                        [styles.buttonLight]: theme === 'light'
                  })}
                  onClick={onClick}
            >
                  {children}
            </button>
      )
}
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