I’ve seen some PowerShell scripts that do this–but the author of the article said it only disables new alerts.
We have a user that wants to temporarily disable alerts to do some maintenance on the list (add fields) without 300 users receiving emails.
Is there javascript we could put in a content editor. Not totally certain of where to put it.
There are multiple way you can do that, details are below in this blog, which ever way you are comfortable. From central admin, for each
http://sharepointchips.com/2015/06/647/
You can use the following stsadm command to disable alerts temporarily.
 stsadm -o setproperty -pn alerts-enabled -pv False -url <site url>
To enable the alerts use the following:
 stsadm -o setproperty -pn alerts-enabled -pv True -url <site url>
