Hi John
As HSRP is Cisco Proprietary you can use the standard VRRP protocol to do the same on EX switches.
Here is a sample config lets say on two central switches:
Switch A:
set interfaces ge-0/0/0 unit 0 family ethernet-switching vlan members V1
set interfaces ge-0/0/1 unit 0 family ethernet-switching vlan members V1
set interfaces vlan unit 1 family inet address 10.0.0.254/24
set interfaces vlan unit 1 family inet address 10.0.0.254/24 vrrp-group 0 virtual-address 10.0.0.252
set interfaces vlan unit 1 family inet address 10.0.0.254/24 vrrp-group 0 priority 110
set vlans V1 l3-interface vlan.1
Switch B:
set interfaces ge-0/0/0 unit 0 family ethernet-switching vlan members V1
set interfaces ge-0/0/1 unit 0 family ethernet-switching vlan members V1
set interfaces vlan unit 1 family inet address 10.0.0.253/24
set interfaces vlan unit 1 family inet address 10.0.0.253/24 vrrp-group 0 virtual-address 10.0.0.252
set vlans V1 l3-interface vlan.1
In this case you have Switch A and B that have their two interfaces ge-0/0/0 and ge-0/0/1 in the same vlan (vlan V1) and share a virtual address on it (10.0.0.252) that can be the default gateway.
Switch A is the master as it has a changed default priority to 110 the default (on B) is 100.
Hope this will help you!