add css value with js code example

Example 1: add style javascript

// Bad:
element.setAttribute("style", "background-color: red;");
// Good:
element.style.backgroundColor = "red";

Example 2: how to give css style in javascript

document.getElementById("myH1").style.color = "red";

Example 3: adding styling to element using javascript

var elem = document.querySelector('#some-element');

// Set color to purple
elem.style.color = 'purple';

// Set the background color to a light gray
elem.style.backgroundColor = '#e5e5e5';

// Set the height to 150px
elem.style.height = '150px';

Example 4: add css in javascript

document.getElementById("demo").style.display = "none";

Example 5: change color of css in js

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Change the Background Color with JavaScript</title>
<script>
    // Function to change webpage background color
    function changeBodyBg(color){
        document.body.style.background = color;
    }
    
    // Function to change heading background color
    function changeHeadingBg(color){
        document.getElementById("heading").style.background = color;
    }
</script>
</head>
<body>
    <h1 id="heading">This is a heading</h1>
    <p>This is a paragraph of text.</p>
    <hr>
    <div>
        <label>Change Webpage Background To:</label>
        <button type="button" onclick="changeBodyBg('yellow');">Yellow</button>
        <button type="button" onclick="changeBodyBg('lime');">Lime</button>
        <button type="button" onclick="changeBodyBg('orange');">Orange</button>
    </div>
    <br>
    <div>
        <label>Change Heading Background To:</label>
        <button type="button" onclick="changeHeadingBg('red');">Red</button>
        <button type="button" onclick="changeHeadingBg('green');">Green</button>
        <button type="button" onclick="changeHeadingBg('blue');">Blue</button>
    </div>
</body>
</html>

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Css Example