When i bought an item with attack speed on jhin, hes base attackspeed didnt went up/same with runes

Jhin's attack speed stats scale into his damage, and not into his attack speed. Check out Jhin's Champion Reveal page for more information about his skills and passive!

Jhin’s crits deal less damage than normal, and his attack speed doesn’t actually scale with attack speed. Instead, Jhin gains attack damage from any attack speed and crit chance he earns through itemization and runes, while crits give him a burst of movement based on his attack speed.

Read Jhin's passive. He doesn't gain bonus ATK speed. Instead any bonus ATK speed he has gained through runes/masteries and items instead converts into extra AD. Take a read of his passive and then you should understand a bit more.