To change placeholder text with JavaScript, we set the placeholder
property.
For instance, we write
<input type="text" name="Email" placeholder="Some Text" />
to add an input.
Then we write
document.getElementsByName("Email")[0].placeholder = "new text for email";
to select the input with getElementsByName
and get the first element from the returned node list.
And then we set the placeholder
property to the new placeholder
attribute value.