how to access individual elements of innerhtml in javascript code example

Example 1: javascript innerhtml

document.getElementById("example").innerHTML = "Paragraph changed!";

Example 2: innerhtml in javascript

<p id="demo" class="demo_class"></p>

<script>
//simple
document.getElementById("demo").innerHTML = "hello World";

//advance
document.getElementById("demo").innerHTML = person("ahsan", "21");

function person(name1, age1) {
    return ("Your name is " + name1 + ". You're " + age1 + " years old.");
}

</script>