If you can use Nintex, use it (you can do it easily).
Create one form for each content Types. In the form desiner, when you open property of your field, in Advence section, you can set the control mode of your field. So set the control mode of your field to : Display. And when the form is open in edit, your field will be in Read Only.If you can use Nintex, use it (you can do it easily).
Create one form for each content Types. In the form desiner, when you open property of your field, in Advence section, you can set the control mode of your field. So set the control mode of your field to : Display. And when the form is open in edit, your field will be in Read Only.
If you want to use only JS, there is a simple Lib SPutility JS to do this, but you need to "dev" it
Hope this help you