动画前进后过渡不起作用

Question

Hie!

Transition doesn't work after animation with animation-fill-mode: forwards; First animation fires and ends on hover, but then after unhovering transition doesn't apply.

Codepen here

It reproduces in chrome and safari. In firefox works fine.

pug:

button Button

scss:

body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

button {
  padding: 5px 0;
  position: relative;
  border: none;
  border-radius: 0;
  background: transparent;
  outline: none;
  cursor: pointer;
  font-weight: 700;
  text-transform: uppercase;

  &:before {
    content: '';
    position: absolute;
    bottom: 0;
    left: 100%;
    right: 0;
    height: 4px;
    border-radius: 2px;
    background: blue;
    transition: all .25s;
  }

  &:hover {

    &:before {
      animation: nav-link-hover .25s forwards;
    }
  }
}

@keyframes nav-link-hover {

    0% {
        left: 0;
        right: 100%;
    }

    100% {
        left: 0;
        right: 0;
    }
}

UPDATE
I've found workaround but will wait for any answer and gladly accept it if it will be better or for example successfully uses broken keyframes.

Answer 1

Still don't know what's wrong with keyframes in chrome/safari, but have found simple workaround.

Now first 'before'-element is on right with no width right: 0; width: 0; right: 0; width: 0; .
On hover it moves to left with 100% width, that begins to transitionally grow: left: 0; right: auto; width: 100%; left: 0; right: auto; width: 100%; .
Finally, when hover was lost, 'before' starts to decreasing, resting on the right end again.

New code:

button {
  padding: 5px 0;
  position: relative;
  border: none;
  border-radius: 0;
  background: transparent;
  outline: none;
  cursor: pointer;
  font-weight: 700;
  text-transform: uppercase;

  &:before {
    content: '';
    position: absolute;
    bottom: 0;
    right: 0;
    width: 0;
    height: 4px;
    border-radius: 2px;
    background: blue;
    transition: all .25s;
  }

  &:hover {

    &:before {
      left: 0;
      right: auto;
      width: 100%;
    }
  }
}

Codepen

Answer 2

Animating elements require a defined state before the animation begins. If you define a state on a trigger (ie. hover), some unexpected behaviour may occur. Therefore, you should set your starting point before the hover.

In this case, simply move left: 0; from the hover to the "non-hover" properties of &:before

button {
  padding: 5px 0;
  position: relative;
  border: none;
  border-radius: 0;
  background: transparent;
  outline: none;
  cursor: pointer;
  font-weight: 700;
  text-transform: uppercase;

  &:before {
    content: '';
    position: absolute;
    left: 0;
    bottom: 0;
    right: 0;
    width: 0;
    height: 4px;
    border-radius: 2px;
    background: blue;
    transition: all .25s;
  }

  &:hover {

    &:before {
      right: auto;
      width: 100%;
    }
  }
}