Omitting the parameter returns the current value (getter), whereas defining the parameter sets the value (setter) and returns the instance itself for easier chaining.
GreenSock Docs (HTML5/JS)
TimelineMax
.timeScale()
Factor that's used to scale time in the animation where 1 = normal speed (the default), 0.5 = half speed, 2 = double speed, etc.
Parameters
value: Number
(default = NaN
) — Omitting the parameter returns the current value (getter), whereas defining the parameter sets the value (setter) and returns the instance itself for easier chaining.
Returns : *

Details
Factor that's used to scale time in the animation where 1 = normal speed (the default), 0.5 = half speed, 2 = double speed, etc. For example, if an animation's duration
is 2 but its timeScale
is 0.5, it will take 4 seconds to finish. If you nest that animation in a timeline whose timeScale
is 0.5 as well, it would take 8 seconds to finish. You can even tween the timeScale
to gradually slow it down or speed it up.
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 myAnimation.timeScale(2).play(1);
var currentTimeScale = myAnimation.timeScale(); //gets current timeScale
myAnimation.timeScale( 0.5 ); //sets timeScale to half-speed