how to change <input> value with javascript code example

Example 1: javascript set input field value

document.getElementById("myInputID").value = "My Value"; //set value on myInputID

Example 2: javascript change input value

document.getElementById("ID").value = "Tamer Jarrar";

Example 3: javascript input value change

function updateInput(ish){
    document.getElementById("fieldname").value = ish;
}