I just noticed that when I Press 2 keys And I released one , then the released animation is active and the player goes to the direction.
C2 example Space Blaster game
If you press Left And Right simultaneously and then release Right >>
The space ship is going Left but with the Defaut animation and not the left animation.
For this game difference is quite not visible but in platform you don't want the player to do some bizarre moonwalk and just slide on the ground.
Tried on Chrome + Firefox
Sorry if it has been said already