//disable the button
document.getElementById(BUTTON_ID).disabled = true;
//reable the button
document.getElementById(BUTTON_ID).removeAttribute('disabled');// Makes the button disabled
document.getElementById("myButtonId").setAttribute("disabled", "");
// Removes disabled attribute
document.getElementById("myButtonId").removeAttribute("disabled");//javascript getelementbyid disable
//Enable a button
document.getElementById("Button").disabled=false;
//Disable a button
document.getElementById("Button").disabled=true;