.yoyo()

Gets or sets the timeline’s yoyo state, where true causes the timeline to go back and forth, alternating backward and forward on each repeat. yoyo works in conjunction with repeat, where repeat controls how many times the timeline repeats, and yoyo controls whether or not each repeat alternates direction. So in order to make a timeline yoyo, you must set its repeat to a non-zero value.

Yoyo-ing, has no affect on the timeline’s reversed property. For example, if repeat is 2 and yoyo is false, it will look like: start - 1 - 2 - 3 - 1 - 2 - 3 - 1 - 2 - 3 - end. But if yoyo is true, it will look like: start - 1 - 2 - 3 - 3 - 2 - 1 - 1 - 2 - 3 - end.

You can set the yoyo property initially by passing yoyo: true in the vars parameter, like: gsap.timeline({repeat: 1, yoyo: true});

This method serves as both a getter and setter. Omitting the parameter returns the current value (getter), whereas defining the parameter sets the value (setter) and returns the instance itself for easier chaining, like myTimeline.yoyo(true).repeat(3).timeScale(2).play(0.5);

var yoyo = myTimeline.yoyo(); //gets current yoyo state
myTimeline.yoyo( true ); //sets yoyo to true