Jumping spiders (family Salticidae) are active hunters. They don’t rely on webs to capture prey, they ambush it. They’re capable of leaping several times their own body length in this endeavor. Just prior to jumping, they attach a strand of silk to their location. If they happen to fall, they climb back up the silk and resume hunting.
The fact that this spider captured a katydid (family Tettigoniidae) is a testament to their hunting ability. Katydids are far superior jumpers, and it would have been easy for it to escape if it could react fast enough.
Jumping spiders are really quick, however, and this katydid was taken by surprise. In addition to their speed, these spiders have excellent vision which is made possible in part by their two very large center eyes.