There is a way to disable all your fields control in form through javascript.
function disableAllFields(executionContext) {
try {
var formContext = executionContext.getFormContext();
var status = formContext.getAttribute("new_status").getValue();
if (parseInt(status) != 275380000 ) { //completed --> If you want to disable based on condition.
var formContext = executionContext.getFormContext();
formContext.ui.controls.forEach(function (control, i) {
if (control && control.getDisabled && !control.getDisabled()) {
control.setDisabled(true);
}
});
}
}
catch (err) {
}
}
The function is now ready now you can use this function on page load, on field change event.