Question on how to add a "dash" ability to sidescroller

I tried finding something similiar, though haven't managed to, so I got to ask here instead.

I'm trying to add a "dash" ability to my 2.5D sidescroller, meaning that basicly on the press of a button, the character moves in a straight line to the right/left (depending where he faces, or which key is pressed, that is both possible). The distance is allways the same, no matter how long the button is pressed and it plays a proper animation. More so, enemies will only be defeatable by being dashed-through. But I think I can handle that later with a boolean and some if-statements.

My current problem is, how could I make such an ability? Especially not with a teleportation, but just a dash?