JavaScript Can Change HTML Content

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”;

JavaScript Can Change HTML Attribute Values

In this example JavaScript changes the value of the src (source) attribute of an <img> tag:

JavaScript Can Change HTML Styles (CSS)

Changing the style of an HTML element, is a variant of changing an HTML attribute:

document.getElementById(“demo”).style.fontSize=“35px”;