JavaScript/class5imp.html at master · vishal-vaish/JavaScript · GitHub

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<!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>
    <div>
        <p class="para">This is paragraph</p>
        <p class="blue">This is a paragraph with blue class</p>
        <p class="blue">This is a paragraph with blue class</p>
        <p class="green">This is a paragraph with green class</p>
    </div>
</body>
</html>
<script>
    function changebackgroundColor(){
     // to select by class
    //   const para=document.getElementsByClassName("blue");
        const para=document.getElementsByClassName("green");
        console.log("Paragraph are:",para);

    // to select by paragraph
    const para1=document.getElementsByTagName("p");
        console.log("Paragraph are:",para1);

// to select the element with id

const para2=document.querySelector("blue");
// only return first element matching the criteria

//const para2=document.querySelectorAll("blue");
// to select all element matching the criteria
console.log("Paragraph are:",para2);
    }

    changebackgroundColor();
</script>