How can I disable any(either custom or standard) button after performing its action?

Hi Pranav,Try the below code that helps you to disable and enable the button.

My Button

Disable "My Button"
Undisable "My Button"

function disableBtn() {
document.getElementById("myBtn").disabled = true;
}

function undisableBtn() {
document.getElementById("myBtn").disabled = false;
}