Easy markup for react-transition-group

For when you don't feel like googling that weird pattern react-transition-group and its variants use every dang time.

Handles one or multiple class/id names, timings, and eases.

@import '../node_modules/scss-react-transition/scss-react-transition.scss';

@include transition('test #test2', (opacity: (0.01, 1), max-height: (0, 30px, 20px)), 150 0.1s, ease ease-out);

yields:

.test-enter, #test2-enter {
  opacity: 0.01;
  max-height: 0;
}

.test-enter.test-enter-active, #test2-enter#test2-enter-active {
  opacity: 1;
  max-height: 30px;
  transition: 150ms ease;
}

.test-exit, .test-leave, #test2-exit, #test2-leave {
  opacity: 1;
  max-height: 20px;
}

.test-exit.test-exit-active, .test-leave.test-leave-active, #test2-exit#test2-exit-active, #test2-leave#test2-leave-active {
  opacity: 0.01;
  max-height: 0;
  transition: 0.1s ease-out;
}

(It does both -exit and -leave for the out transitions because they changed the class names in the React 16 version.)

Argument	Default value	Default unit	Required
Classnames	none	string or list	yes
Props	none	list	yes
Transition time	150ms	ms if unitless, accepts s	no
Transition ease	ease	an ease type	no

Intro animation only

Play only the intro animation by setting a property's third argument to null:

@include transition('introOnly', (transform: (translateY(-10px), initial, null)));

.introOnly-enter {
  transform: translateY(-10px);
}

.introOnly-enter.introOnly-enter-active {
  transform: initial;
  transition: 150ms ease;
}