var context = SP.ClientContext.get_current()
var web = context.get_web()
var actions = web.get_userCustomActions();

context.load(actions)
context.executeQueryAsync(
  function () {
  console.log('Success')
	  	var enumerator = actions.getEnumerator();
		while (enumerator.moveNext()) {
			var action = enumerator.get_current();
			console.log(action.get_location() + " | " + action.get_description() + " | " + action.get_scriptBlock())
		}
},
function () {
  console.log('Error')
})