One of many JavaScript HTML methods is getElementById().
This example uses the method to “find” an HTML element (with id=”demo”) and changes the element content (innerHTML) to “Hello JavaScript”:
document.getElementById("demo").innerHTML = "Hello JavaScript";
In this example JavaScript changes the value of the src (source) attribute of an <img> tag:
Changing the style of an HTML element, is a variant of changing an HTML attribute:
document.getElementById("demo").style.fontSize = "35px";
or
document.getElementById('demo').style.fontSize = '35px';
Hiding HTML elements can be done by changing the display style:
document.getElementById("demo").style.display = "none";
or
document.getElementById('demo').style.display = 'none';