I have created a fixed navbar. Now I am trying to change background color navbar. I have created a fixed menu with changing color when scrolling down at the end of the page.

import React, { Component } from 'react';
import { Collapse, Container, Navbar, NavbarBrand, NavbarToggler, NavItem, NavLink } from 'reactstrap';
import { Link } from 'react-router-dom';
import { LoginMenu } from './api-authorization/LoginMenu';
import mainImage from './logoblue.png';

export class NavMenu extends Component {
    static displayName = NavMenu.name;

    constructor(props) {
        super(props);

        this.toggleNavbar = this.toggleNavbar.bind(this);
        this.state = {
            collapsed: true
        };
    }

    toggleNavbar() {
        this.setState({
            collapsed: !this.state.collapsed
        });
    }

    render() {
        return (
            <header>
                <Navbar className="navbar-expand-sm navbar-toggleable-sm fixed-top ng-white border-bottom box-shadow bg-white" light>
                    <Container>
                        <NavbarBrand tag={Link} to="/">
                            <img src={mainImage} style={{ height: '55px' }} alt="Logo" />
                        </NavbarBrand>
                        <NavbarToggler onClick={this.toggleNavbar} className="mr-2" />
                        <Collapse className="d-sm-inline-flex flex-sm-row-reverse" isOpen={!this.state.collapsed} navbar>
                            <ul className="navbar-nav flex-grow">

                                <LoginMenu>
                                </LoginMenu>
                            </ul>
                        </Collapse>
                    </Container>
                </Navbar>
            </header>
        );
    }
}

I have created a fixed navbar. Now I am trying to change background color navbar. I have created a fixed menu with changing color when scrolling down at the end of the page.

import React, { Component } from 'react';
import { Collapse, Container, Navbar, NavbarBrand, NavbarToggler, NavItem, NavLink } from 'reactstrap';
import { Link } from 'react-router-dom';
import { LoginMenu } from './api-authorization/LoginMenu';
import mainImage from './logoblue.png';

export class NavMenu extends Component {
    static displayName = NavMenu.name;

    constructor(props) {
        super(props);

        this.toggleNavbar = this.toggleNavbar.bind(this);
        this.state = {
            collapsed: true
        };
    }

    toggleNavbar() {
        this.setState({
            collapsed: !this.state.collapsed
        });
    }

    render() {
        return (
            <header>
                <Navbar className="navbar-expand-sm navbar-toggleable-sm fixed-top ng-white border-bottom box-shadow bg-white" light>
                    <Container>
                        <NavbarBrand tag={Link} to="/">
                            <img src={mainImage} style={{ height: '55px' }} alt="Logo" />
                        </NavbarBrand>
                        <NavbarToggler onClick={this.toggleNavbar} className="mr-2" />
                        <Collapse className="d-sm-inline-flex flex-sm-row-reverse" isOpen={!this.state.collapsed} navbar>
                            <ul className="navbar-nav flex-grow">

                                <LoginMenu>
                                </LoginMenu>
                            </ul>
                        </Collapse>
                    </Container>
                </Navbar>
            </header>
        );
    }
}

• javascript
• reactjs
• bootstrap-4

• What exactly are you trying to do? – Mayank Bansal Commented Jan 2, 2020 at 7:30
• When Scroll navbar background color change to yellow – Pritesh Bhoi Commented Jan 2, 2020 at 7:35
• @Pritesh So you mean when scrolling at the bottom of your page, the navbar changes color to yellow? – minus.273 Commented Jan 2, 2020 at 8:02
• 1 @minus.273 Yup! – Pritesh Bhoi Commented Jan 2, 2020 at 10:43

2 Answers 2

I have created a demo for you. Hope it can help!

class App extends React.Component{
  state ={className:"" };
  
  componentDidMount(){
    window.addEventListener("scroll", this.handleScroll);
  }
  
  handleScroll=()=>{
    if (window.pageYOffset > 0) {
        if(!this.state.className){
          this.setState({ className: "blue" });   
        }
    }else{
        if(this.state.className){
          this.setState({ className: "" });
        }
    }
   
  }
  
  render(){
    return(
      <main>
        <header ref={(r)=>this.ref=r} className={this.state.className}>Header</header>
        <div>
         Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lorem Ipsum passage, and going through the cites of the word in classical literature, discovered the undoubtable source. Lorem Ipsum comes from sections 1.10.32 and 1.10.33 of "de Finibus Bonorum et Malorum" (The Extremes of Good and Evil) by Cicero, written in 45 BC. This book is a treatise on the theory of ethics, very popular during the Renaissance. The first line of Lorem Ipsum, "Lorem ipsum dolor sit amet..", comes from a line in section 1.10.32.

The standard chunk of Lorem Ipsum used since the 1500s is reproduced below for those interested. Sections 1.10.32 and 1.10.33 from "de Finibus Bonorum et Malorum" by Cicero are also reproduced in their exact original form, accompanied by English versions from the 1914 translation by H. Rackham.
Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lorem Ipsum passage, and going through the cites of the word in classical literature, discovered the undoubtable source. Lorem Ipsum comes from sections 1.10.32 and 1.10.33 of "de Finibus Bonorum et Malorum" (The Extremes of Good and Evil) by Cicero, written in 45 BC. This book is a treatise on the theory of ethics, very popular during the Renaissance. The first line of Lorem Ipsum, "Lorem ipsum dolor sit amet..", comes from a line in section 1.10.32.

The standard chunk of Lorem Ipsum used since the 1500s is reproduced below for those interested. Sections 1.10.32 and 1.10.33 from "de Finibus Bonorum et Malorum" by Cicero are also reproduced in their exact original form, accompanied by English versions from the 1914 translation by H. Rackham.
Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lorem Ipsum passage, and going through the cites of the word in classical literature, discovered the undoubtable source. Lorem Ipsum comes from sections 1.10.32 and 1.10.33 of "de Finibus Bonorum et Malorum" (The Extremes of Good and Evil) by Cicero, written in 45 BC. This book is a treatise on the theory of ethics, very popular during the Renaissance. The first line of Lorem Ipsum, "Lorem ipsum dolor sit amet..", comes from a line in section 1.10.32.

The standard chunk of Lorem Ipsum used since the 1500s is reproduced below for those interested. Sections 1.10.32 and 1.10.33 from "de Finibus Bonorum et Malorum" by Cicero are also reproduced in their exact original form, accompanied by English versions from the 1914 translation by H. Rackham.
Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lorem Ipsum passage, and going through the cites of the word in classical literature, discovered the undoubtable source. Lorem Ipsum comes from sections 1.10.32 and 1.10.33 of "de Finibus Bonorum et Malorum" (The Extremes of Good and Evil) by Cicero, written in 45 BC. This book is a treatise on the theory of ethics, very popular during the Renaissance. The first line of Lorem Ipsum, "Lorem ipsum dolor sit amet..", comes from a line in section 1.10.32.

The standard chunk of Lorem Ipsum used since the 1500s is reproduced below for those interested. Sections 1.10.32 and 1.10.33 from "de Finibus Bonorum et Malorum" by Cicero are also reproduced in their exact original form, accompanied by English versions from the 1914 translation by H. Rackham.
Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lorem Ipsum passage, and going through the cites of the word in classical literature, discovered the undoubtable source. Lorem Ipsum comes from sections 1.10.32 and 1.10.33 of "de Finibus Bonorum et Malorum" (The Extremes of Good and Evil) by Cicero, written in 45 BC. This book is a treatise on the theory of ethics, very popular during the Renaissance. The first line of Lorem Ipsum, "Lorem ipsum dolor sit amet..", comes from a line in section 1.10.32.

The standard chunk of Lorem Ipsum used since the 1500s is reproduced below for those interested. Sections 1.10.32 and 1.10.33 from "de Finibus Bonorum et Malorum" by Cicero are also reproduced in their exact original form, accompanied by English versions from the 1914 translation by H. Rackham.
Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lorem Ipsum passage, and going through the cites of the word in classical literature, discovered the undoubtable source. Lorem Ipsum comes from sections 1.10.32 and 1.10.33 of "de Finibus Bonorum et Malorum" (The Extremes of Good and Evil) by Cicero, written in 45 BC. This book is a treatise on the theory of ethics, very popular during the Renaissance. The first line of Lorem Ipsum, "Lorem ipsum dolor sit amet..", comes from a line in section 1.10.32.

The standard chunk of Lorem Ipsum used since the 1500s is reproduced below for those interested. Sections 1.10.32 and 1.10.33 from "de Finibus Bonorum et Malorum" by Cicero are also reproduced in their exact original form, accompanied by English versions from the 1914 translation by H. Rackham.
Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lorem Ipsum passage, and going through the cites of the word in classical literature, discovered the undoubtable source. Lorem Ipsum comes from sections 1.10.32 and 1.10.33 of "de Finibus Bonorum et Malorum" (The Extremes of Good and Evil) by Cicero, written in 45 BC. This book is a treatise on the theory of ethics, very popular during the Renaissance. The first line of Lorem Ipsum, "Lorem ipsum dolor sit amet..", comes from a line in section 1.10.32.

The standard chunk of Lorem Ipsum used since the 1500s is reproduced below for those interested. Sections 1.10.32 and 1.10.33 from "de Finibus Bonorum et Malorum" by Cicero are also reproduced in their exact original form, accompanied by English versions from the 1914 translation by H. Rackham.
Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lorem Ipsum passage, and going through the cites of the word in classical literature, discovered the undoubtable source. Lorem Ipsum comes from sections 1.10.32 and 1.10.33 of "de Finibus Bonorum et Malorum" (The Extremes of Good and Evil) by Cicero, written in 45 BC. This book is a treatise on the theory of ethics, very popular during the Renaissance. The first line of Lorem Ipsum, "Lorem ipsum dolor sit amet..", comes from a line in section 1.10.32.

The standard chunk of Lorem Ipsum used since the 1500s is reproduced below for those interested. Sections 1.10.32 and 1.10.33 from "de Finibus Bonorum et Malorum" by Cicero are also reproduced in their exact original form, accompanied by English versions from the 1914 translation by H. Rackham.
        </div>
      </main>
    );
  }
}

ReactDOM.render(<App/>, document.getElementById("root"));

body{  
  padding:0;
  margin:0;
}
header{
  height: 70px;
  background: #ccc;
  position:sticky;
  top:0;
  width:100%;
  transition:0.5s;
}

header.blue{
  background: blue;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<div id="root"></div>

first remove bg-white from this line:

 <Navbar className="navbar-expand-sm navbar-toggleable-sm fixed-top ng-white border-bottom box-shadow bg-white" light>

then style your Navbar backgroundColor whenever you want. in scrolling or ... like :

 <Navbar style={{backgroundColor: '#a83248'}} className="navbar-expand-sm navbar-toggleable-sm fixed-top ng-white border-bottom box-shadow " light>

or use standard class name like:

bg-primary
bg-light
bg-success
bg-info
bg-warning
bg-danger
bg-dark

sample output: https://codesandbox.io/s/nav-bar-examples-68xfg