It never occured to me to use it for indexOf, but if it works, that's nice. I usually use a bitwise OR as a faster alternative to Math.floor:
1.324324|0 // 1
Well, it's not exactly floor, as it will just cut of everything after the dot, but if you're only dealing with positive number it does the job and has the nice side effect of converting non-numbers into 0:
Guild Leader: Ladies,you got a Job for today. You have to Battle with Marauder,only Female must to this Job. F.Magic Knight: So,only Female can do this? Heroine: I can't wait for this! Gunner Lady: Well,i can use the Seduction Skill to them,It's effective for Male Target F.Knight: You always use that?