;<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <p class="title">Text1</p>
    <p class="title">Text2</p>
    <p class="title">Text3</p>
    <p class="title">Text4</p>
    <p class="title">Text5</p>
    <p class="title">Text6</p>
    <p class="title">Text7</p>
    <p class="title">Text8</p>
    <p class="title">Text9</p>
    <p class="title">Text10</p>
</body>
<style>
    .title{
        background-color: red;
        display: inline-block;
        padding: 10px;
      cursor:pointer;
    }
    .title.active{
        background: green;
    }
</style>
<script>
    let titles = Array.from(document.querySelectorAll(".title"))
    titles.forEach(function(it){
it.onclick = function(){
    it.classList.toggle("active")
}
    })
</script>
</html>

External CSS

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External JavaScript

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