javascript/project1(change_background).html at main · itshoax/javascript · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>change background</title>
</head>
<body>
    <button onclick="background()" class="button" id="button">Click Me</button>
    <style>
        *{
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }


        body{
            background-color: #ff70fb;
        }
        .button{
            border: 0;
            background-color: #1eff44;
            border-radius: 5px;
            padding: 10px 20px;
            display: block;
            margin: 2rem auto;
            font-family: sans-serif;
            outline: none;
            cursor: pointer;
            font: 1em sans-serif;
            color: blue;
        }


        #button {
            text-decoration: none;
        }


        .button:hover {
            background-color: #ff70fb;
            transition: 1s;
        }

    </style>
            <script>
                function background() {
                    alert("It is working");
                    //to target an element by class you have to use index of it like in this case [0]
                    document.getElementsByClassName("button")[0].style.color = "white";
                    //you also have to use index in tagname
                    document.getElementsByTagName("body")[0].style.backgroundColor = "black";
                    //you don't have to use index in id as id is unique
                    document.getElementById("button").style.textDecoration = "underline";
                }

             </script>
              </body>
</html>