`Changing the background according to the page URL in React JS: A guide`

Question

`Changing the background according to the page URL in React JS: A guide`

Looking to enhance my simple app with a few pages by changing the background color based on page URL using React.js.

What I aim to achieve:

If the pathname is /movies, I want the background color to be red.

This is my current progress:

 import React, { useState } from 'react';

function Testing() {
    const [moviesUrlBackgroundColor, setMoviesUrlBackgroundColor] = useState('green');
    const getMoviesUrl = window.location.pathname;

    if (getMoviesUrl === '/movies') {
        setMoviesUrlBackgroundColor('red');
    } else {
        setMoviesUrlBackgroundColor('green');
    }

    return (
        <div>
            <Container style={{backgroundColor: moviesUrlBackgroundColor}}>
                Testing
            </Container>
        </div>
    );
}

export default Testing;

const Container = styled.div`
    background-color: green;
`;

However, I am encountering the following issue:

app.js:38323 Uncaught Invariant Violation: Too many re-renders. React limits the number of renders to prevent an infinite loop.

How can I resolve this problem and make it work as intended?

javascript css reactjs react-router

Answer 1

Answer №1

It is advisable to add an additional check to ensure that the background color has been properly set in your code. The current implementation is causing an infinite rerender loop.

 import React from 'react'

 function Testing() {
 const[moviesUrlBackgroundColor, setMoviesUrlBackgroundColor] = useState('green');
 const [bgFlag, setbgFlag] = useState(false);


 const getMoviesUrl = window.location.pathname;

 if(!bgFlag){
     setMoviesUrlBackgroundColor(getMoviesUrl == '/movies' ? 'red' : 'green')
     setbgFlag(true)
 }

return (
    <div>
        <Container style={{backgroundColor:moviesUrlBackgroundColor}}>
        
            Testing
        </Container>
    </div>
)
 }

 export default Testing

const Container = styled.div`
    background-color:green
`;

Answer 2

It is advisable to add an additional check to ensure that the background color has been properly set in your code. The current implementation is causing an infinite rerender loop.

 import React from 'react'

 function Testing() {
 const[moviesUrlBackgroundColor, setMoviesUrlBackgroundColor] = useState('green');
 const [bgFlag, setbgFlag] = useState(false);


 const getMoviesUrl = window.location.pathname;

 if(!bgFlag){
     setMoviesUrlBackgroundColor(getMoviesUrl == '/movies' ? 'red' : 'green')
     setbgFlag(true)
 }

return (
    <div>
        <Container style={{backgroundColor:moviesUrlBackgroundColor}}>
        
            Testing
        </Container>
    </div>
)
 }

 export default Testing

const Container = styled.div`
    background-color:green
`;

Answer 3

Answer №2

Implementing an useEffect block allows for efficient handling of side-effects.

  useEffect(() => {
    if(getMoviesUrl === '/movies'){
      console.log("execution")
        setMoviesUrlBackgroundColor('red');
    }else{
        setMoviesUrlBackgroundColor('green');
    }
  },[getMoviesUrl]);

Answer 4

Implementing an useEffect block allows for efficient handling of side-effects.

  useEffect(() => {
    if(getMoviesUrl === '/movies'){
      console.log("execution")
        setMoviesUrlBackgroundColor('red');
    }else{
        setMoviesUrlBackgroundColor('green');
    }
  },[getMoviesUrl]);

Answer 5

Answer №3

The issue arises when you invoke the setMoviesUrlBackgroundColor function without encapsulating it within an effect, leading to a recursive call.

To resolve this issue, simply update the state whenever the pathname changes:

React.useEffect(() => {
  if (getMoviesUrl === '/movies') {
    setMoviesUrlBackgroundColor('red');
  } else {
    setMoviesUrlBackgroundColor('green');
  }
}, [getMoviesUrl])

Answer 6

The issue arises when you invoke the setMoviesUrlBackgroundColor function without encapsulating it within an effect, leading to a recursive call.

To resolve this issue, simply update the state whenever the pathname changes:

React.useEffect(() => {
  if (getMoviesUrl === '/movies') {
    setMoviesUrlBackgroundColor('red');
  } else {
    setMoviesUrlBackgroundColor('green');
  }
}, [getMoviesUrl])

Answer 7

Answer №4

Ah-ha! I see what's happening here. Looks like you've accidentally created an infinite loop in your first if statement:

if (getMoviesUrl == '/movies') {
    // The issue is that every time the state changes, it triggers a re-render
    // And during each re-render, the state gets changed AGAIN, causing an infinite loop
    setMoviesUrlBackgroundColor('red');
}

My suggestion would be to utilize react-route and fetch the URL from params. Then, update the background color within componentDidMount or useEffect hook when the component mounts for the first time, thus avoiding any potential infinite loops.

Answer 8

Ah-ha! I see what's happening here. Looks like you've accidentally created an infinite loop in your first if statement:

if (getMoviesUrl == '/movies') {
    // The issue is that every time the state changes, it triggers a re-render
    // And during each re-render, the state gets changed AGAIN, causing an infinite loop
    setMoviesUrlBackgroundColor('red');
}

My suggestion would be to utilize react-route and fetch the URL from params. Then, update the background color within componentDidMount or useEffect hook when the component mounts for the first time, thus avoiding any potential infinite loops.

Answer 9

Answer №5

Each time the page renders, `window.location.pathname` was causing the state to reset. To avoid unnecessary re-renders, this should be placed inside the `useEffect` hook.

Another suggestion is to pass `props` to your styled component for better customization. I have included an example in the code below.

For a detailed solution, you can check out my codesandbox project: https://codesandbox.io/s/musing-mirzakhani-njmsh?file=/src/random.js:0-620

import React, { useState, useEffect } from "react";
import styled from "styled-components";

const Container = styled.div`
  background: ${(props) => props.backgroundColor || "green"};
`;

const Testing = () => {
  const [moviesUrlBackgroundColor, setMoviesUrlBackgroundColor] = useState(
    "green"
  );

  useEffect(() => {
    const getMoviesUrl = window.location.pathname;
    if (getMoviesUrl === "/movies") {
      setMoviesUrlBackgroundColor("yellow");
    }
  }, [moviesUrlBackgroundColor]);

  return (
    <div>
      <Container backgroundColor={moviesUrlBackgroundColor}>Test</Container>
    </div>
  );
};

export default Testing;

Cheers!

Answer 10

Each time the page renders, `window.location.pathname` was causing the state to reset. To avoid unnecessary re-renders, this should be placed inside the `useEffect` hook.

Another suggestion is to pass `props` to your styled component for better customization. I have included an example in the code below.

For a detailed solution, you can check out my codesandbox project: https://codesandbox.io/s/musing-mirzakhani-njmsh?file=/src/random.js:0-620

import React, { useState, useEffect } from "react";
import styled from "styled-components";

const Container = styled.div`
  background: ${(props) => props.backgroundColor || "green"};
`;

const Testing = () => {
  const [moviesUrlBackgroundColor, setMoviesUrlBackgroundColor] = useState(
    "green"
  );

  useEffect(() => {
    const getMoviesUrl = window.location.pathname;
    if (getMoviesUrl === "/movies") {
      setMoviesUrlBackgroundColor("yellow");
    }
  }, [moviesUrlBackgroundColor]);

  return (
    <div>
      <Container backgroundColor={moviesUrlBackgroundColor}>Test</Container>
    </div>
  );
};

export default Testing;

Cheers!

`Changing the background according to the page URL in React JS: A guide`

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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