Keep selected theme on page refresh using HTML, CSS and JavaScript-CodePudding

I would like to keep the selected theme when refreshing the page as well as across all other pages. I've seen other examples but I don't know how to implement it in the code as I'm quite newbie. I've included the code of the functionality so far. Many thanks in advance.

function changeTheme(bgColor, textColor) {
  var styles = document.documentElement.style;
  styles.setProperty('--bg-color', bgColor);
  styles.setProperty('--text-color', textColor);
}

var dark = document.querySelector('#dark');
var light = document.querySelector('#light');
var blue = document.querySelector('#blue');

dark.addEventListener('click', function() {
  changeTheme('#333', 'white');
});

light.addEventListener('click', function() {
  changeTheme('white', 'black');
});

blue.addEventListener('click', function() {
  changeTheme('#2982F5', 'white');
});

:root {
  --bg-color: #333;
  --text-color: white;
}

body {
  font-family: sans-serif;
  background: #c0c0c0;
}

nav {
  color: var(--text-color);
  background: var(--bg-color);
}

ul {
  display: flex;
  justify-content: center;
  align-items: center;
  list-style-type: none;
}

li {
  margin-left: 15px;
}

a {
  color: var(--text-color);
}

<nav>
  <ul>
    <p>Select theme:</p>
    <li>
      <a href="#" id="dark">Dark</a>
    </li>
    <li>
      <a href="#" id="light">Light</a>
    </li>
    <li>
      <a href="#" id="blue">Blue</a>
    </li>
  </ul>
</nav>

CodePudding user response：

For that you could use localStorage. Keep your HTML and CSS code as they are. Your JavaScript code could be like so :

// get stored theme on load
let storedTheme = localStorage.getItem("theme");
if(storedTheme){
 storedTheme= JSON.parse(storedTheme);
 changeTheme(storedTheme.bgColor, storedTheme.textColor);
}

function changeTheme(bgColor, textColor) {
  // updtate stored data when there is a click
  localStorage.setItem("theme", JSON.stringify({bgColor:bgColor, textColor:textColor}));
  var styles = document.documentElement.style;
  styles.setProperty('--bg-color', bgColor);
  styles.setProperty('--text-color', textColor);
}

var dark = document.querySelector('#dark');
var light = document.querySelector('#light');
var blue = document.querySelector('#blue');

dark.addEventListener('click', function() {
  changeTheme('#333', 'white');
});

light.addEventListener('click', function() {
  changeTheme('white', 'black');
});

blue.addEventListener('click', function() {
  changeTheme('#2982F5', 'white');
});

CodePudding user response：

You can set them to local storage and get it in first load

function changeTheme(bgColor, textColor) {
  var styles = document.documentElement.style;
  styles.setProperty('--bg-color', bgColor);
  styles.setProperty('--text-color', textColor);
  localStorage.setItem('bgtheme', bgColor);
  localStorage.setItem('txttheme', textColor);
}

var dark = document.querySelector('#dark');
var light = document.querySelector('#light');
var blue = document.querySelector('#blue');

dark.addEventListener('click', function() {
  changeTheme('#333', 'white');
});

light.addEventListener('click', function() {
  changeTheme('white', 'black');
});

blue.addEventListener('click', function() {
  changeTheme('#2982F5', 'blue');
});

window.onload = (event) => {  
  let bgColor = localStorage.getItem('bgtheme');
  let txtColor = localStorage.getItem('txttheme');
  changeTheme(bgColor, txtColor);
};

:root {
  --bg-color: #333;
  --text-color: white;
}

body {
  font-family: sans-serif;
  background: #c0c0c0;
}

nav {
  color: var(--text-color);
  background: var(--bg-color);
}

ul {
  display: flex;
  justify-content: center;
  align-items: center;
  list-style-type: none;
}

li {
  margin-left: 15px;
}

a {
  color: var(--text-color);
}

<nav>
  <ul>
    <p>Select theme:</p>
    <li>
      <a href="#" id="dark">Dark</a>
    </li>
    <li>
      <a href="#" id="light">Light</a>
    </li>
    <li>
      <a href="#" id="blue">Blue</a>
    </li>
  </ul>
</nav>

CodePudding user response：

Try this example:

<!doctype html>
<html>
 <head>
  <title>Test</title>
  <meta charset="utf-8">
   <style>
    :root {
     --bg-color: #333;
     --text-color: white;
    }

    body {
     font-family: sans-serif;
     background: #c0c0c0;
    }

    nav {
     color: var(--text-color);
     background: var(--bg-color);
    }

    ul {
     dislpay: flex;
     justify-content: center;
     align-items: center;
     list-style-type: none;
    }

    li {
     margin-left: 15px;
    }

    a {
     color: var(--text-color);
    }
   </style>
 </head>
 <body>

<nav>
 <ul>
  <p>Select theme:</p>
  <li>
   <a href="#" id="dark">Dark</a>
  </li>
  <li>
   <a href="#" id="light">Light</a>
  </li>
  <li>
   <a href="#" id="blue">Blue</a>
  </li>
 </ul>
</nav>
  <script>

const app = () => {
// - - app

const appBgColor = localStorage.getItem('appBgColor')
const appTextColor = localStorage.getItem('appTextColor')

if (appBgColor && appTextColor) {
    changeTheme(appBgColor, appTextColor)
}

function changeTheme(bgColor, textColor) {
    localStorage.setItem('appBgColor', bgColor)
    localStorage.setItem('appTextColor', textColor)
        const styles = document.documentElement.style
        styles.setProperty('--bg-color', bgColor)
        styles.setProperty('--text-color', textColor)
}

const dark = document.getElementById('dark')
const light = document.getElementById('light')
const blue = document.getElementById('blue')

dark.addEventListener('click', () => changeTheme('#333', 'white'))
light.addEventListener('click', () => changeTheme('white', 'black'))
blue.addEventListener('click', () => changeTheme('#2982f5', 'white'))
// - - end app
}

document.addEventListener('DOMContentLoaded', app)
  </script>
 </body>
</html>