code-boxx/0-JS-DYNAMIC-CSS.MD

## 0-JS-DYNAMIC-CSS.MD

      
    Raw
  

              0-JS-DYNAMIC-CSS.MD
            
          
    JAVASCRIPT DYNAMIC CSS


https://code-boxx.com/dynamically-load-replace-css/
https://www.youtube.com/watch?v=DhW3tA-yElw

LICENSE

Copyright by Code Boxx
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

  
## 1a-load-css.html
<!DOCTYPE html>
<html>
  <head>
    <title>Dynamically Load CSS</title>
  </head>
  <body>
    <!-- (A) TEST TEXT BLOCK -->
    <p id="demo">FOO BAR!</p>
    <input type="button" onclick="loadcss()" value="Load CSS">

    <!-- (B) DYNAMICALLY LOAD CSS -->
    <script>
    function loadcss () {
      // (B1) CREATE NEW <LINK> TAG
      var stylesheet = document.createElement("link");
      stylesheet.rel = "stylesheet";
      stylesheet.type = "text/css";
      stylesheet.href = "1b-demo.css";

      // (B2) OPTIONAL - ON SUCCESSFUL LOAD & ERROR
      stylesheet.onload = () => alert("CSS loaded");
      stylesheet.onerror = e => alert("Error loading CSS");

      // (B3) APPEND <LINK> TAG TO <HEAD>
      document.head.appendChild(stylesheet);
    }
    </script>
  </body>
</html>

## 1b-demo.css
#demo {
  font-weight: 700;
  font-size: 2em;
  color: red;
}

## 2-create-css.html
<!DOCTYPE html>
<html>
  <head>
    <title>Dynamically Create CSS</title>
  </head>
  <body>
    <!-- (A) TEST TEXT BLOCK -->
    <p id="demo">FOO BAR!</p>
    <input type="button" onclick="insertcss()" value="Insert CSS">

    <!-- (B) DYNAMICALLY CREATE CSS -->
    <script>
    function insertcss () {
      let stylesheet = new CSSStyleSheet();
      stylesheet.insertRule("#demo { color: red; font-weight: 700; }");
      document.adoptedStyleSheets = [stylesheet];
    }
    </script>
  </body>
</html>

## 3-replace-csss.html
<!DOCTYPE html>
<html>
  <head>
    <title>Dynamically Replace CSS</title>
    <!-- (A) CSS STYLE -->
    <style>
    #demo { color: blue; }
    </style>
  </head>
  <body>
    <!-- (B) TEST TEXT BLOCK -->
    <p id="demo">FOO BAR!</p>
    <input type="button" onclick="replacecss()" value="Replace CSS">

    <!-- (C) DYNAMICALLY REPLACE CSS -->
    <script>
    function replacecss () {
      let stylesheet = document.styleSheets[0];
      stylesheet.deleteRule(0);
      stylesheet.insertRule("#demo { color: red; font-weight: 700; }");
    }
    </script>
  </body>
</html>

## 4-css-var.html
<!DOCTYPE html>
<html>
  <head>
    <title>CSS Variables</title>

    <!-- (A) CSS STYLES -->
    <style>
    /* (A1) CSS VARIABLES */
    :root {
      --demo-color: black;
      --demo-weight: 500;
    }

    /* (A2) USE CSS VARIABLES */
    #demo {
      color: var(--demo-color);
      font-weight: var(--demo-weight);
    }
    </style>
  </head>
  <body>
    <!-- (B) TEST TEXT BLOCK -->
    <p id="demo">FOO BAR!</p>
    <input type="button" onclick="cssvar()" value="Replace CSS Var">

    <!-- (C) DYNAMICALLY CHANGE CSS VAR -->
    <script>
    function cssvar () {
      document.documentElement.style.setProperty("--demo-color", "red");
      document.documentElement.style.setProperty("--demo-weight", "700");
    }
    </script>
  </body>
</html>
	<!DOCTYPE html>
	<html>
	<head>
	<title>Dynamically Load CSS</title>
	</head>
	<body>
	<!-- (A) TEST TEXT BLOCK -->
	<p id="demo">FOO BAR!</p>
	<input type="button" onclick="loadcss()" value="Load CSS">

	<!-- (B) DYNAMICALLY LOAD CSS -->
	<script>
	function loadcss () {
	// (B1) CREATE NEW <LINK> TAG
	var stylesheet = document.createElement("link");
	stylesheet.rel = "stylesheet";
	stylesheet.type = "text/css";
	stylesheet.href = "1b-demo.css";

	// (B2) OPTIONAL - ON SUCCESSFUL LOAD & ERROR
	stylesheet.onload = () => alert("CSS loaded");
	stylesheet.onerror = e => alert("Error loading CSS");

	// (B3) APPEND <LINK> TAG TO <HEAD>
	document.head.appendChild(stylesheet);
	}
	</script>
	</body>
	</html>