How to save a dark mode on local storage? – Blancer.com Tutorials and projects

I made a button for dark mode, but when I leave the page, it goes back to light mode. How can I save the user’s choice so that when they go to another page they can continue in the mode they chose?

Js:

let trilho = document.getElementById('trilho')
let body = document.querySelector('body')

trilho.addEventListener('click', ()=>{
    trilho.classList.toggle('dark')
    body.classList.toggle('dark')

})

Css:

*{
    margin: 0;
    padding: 0;
    font-family: 'Poppins', sans-serif;
    box-sizing: border-box;
}

body {
    height: 100px;
    width: 100%;
    background-color: #fafafa;
}

/* DARK MODE */
.trilho {
    width: 70px;
    height: 30px;
    background-color: #6e6d6d;
    border-radius: 70px;
    position: relative;
    cursor: pointer;
}

.trilho .indicador {
    width: 30px;
    height: 30px;
    background-color: #000;
    border-radius: 50%;
    transform: scale(.8);
    position: absolute;
    left: 0;
    transition: .5s;
}

.trilho.dark {
    background-color: #c3c3c3;
}

.trilho.dark .indicador {
    left: 38px;
    background-color: #fff;
}

body.dark .container {
    background-color: #000;
}

body.dark footer {
    background-color: #000;
}

body.dark header {
    background-color: #000;
}

body.dark h1 {
    color: #fff;
}

body.dark a {
    color: #fff;
}

body.dark form{
    box-shadow: none;
}

body.dark .rodape{
    color: #fff;
}

HTML:


    <!DOCTYPE html>
    <html lang="en">
    
    <head>
        <meta http-equiv="X-UA-Compatible" content="ie=edge">
        <meta charset="utf-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>Website</title>
    
        <link rel="stylesheet" type="text/css" href="css/style.css">
        <script src="darkmode.js" async></script>
    
    </head>
    
    <body>
    
        <header>     
            <nav>        
             <ul class="nav-links">
                 <li><a href="/">link</a></li>
                 <li><a href="/">link</a></li>
                 <li><a href="#">link</a></li>
            </ul>    
    
    
          
              <div class="menu-hamb-button hide-on-desktop">
                <div class="btn-line"></div>
                <div class="btn-line"></div>
                <div class="btn-line"></div>
            </div>
           
            </nav>   
    
            <div class="trilho" id="trilho">
                <div class="indicador"></div>
            </div>
     
        </header>
    
        <div class="container">
             <h1>Website</h1>
        </div>
        <footer>
    
        <span class="rodape">Website</span>      
        </footer>
    
    </body>
    </html>

I tried some javascript commands for local storage, but they didn’t work in my html/css, maybe because the way I made my dark mode is different, I don’t know.