From After Effects

After Effects expressions use JavaScript. After Effects supports a modern JavaScript engine and an older Legacy ExtendScript engine. Shrimply expressions use Rhai instead. The concepts are similar, but an After Effects expression must be rewritten rather than pasted directly into Shrimply.

Both systems provide value for the property’s value before the expression, time for time in seconds, and arrays such as [x, y] for multi-component properties. Shrimply also provides t and local_t as aliases for time. In Shrimply, the last value in the script is the result. See Expression basics for every available value and function.

Continuous motion

A simple time calculation is the same in both systems. This rotates by 40 degrees per second:

After EffectsShrimply

time * 40

Variable declarations

Adobe’s expression-language guide shows variables assigned without a declaration keyword. After Effects also supports var in both expression engines and let and const in the modern engine. Translate each form as follows:

After Effects	Expression engines	Shrimply	Meaning
speed = 40	Modern and Legacy	let speed = 40	First definition
var speed = 40	Modern and Legacy	let speed = 40	Mutable variable
let speed = 40	Modern only	let speed = 40	Mutable variable
const speed = 40	Modern only	const speed = 40	Constant

After a Rhai variable has been declared, assign a new value without repeating let:

After EffectsShrimply

speed = 40;
speed = 20;
time * speed

Wiggle and shake

After Effects’ wiggle(frequency, amount) varies around the existing value. Shrimply’s shake(phase) produces smooth noise, so multiply time by the frequency, multiply the noise by the amount, and add it to the original value:

After EffectsShrimply

wiggle(5, 20)

For a 2D property, build the result from x and y. Give each shake call a different seed so the axes move independently:

[
  x + shake(t * 5, 0) * 20,
  y + shake(t * 5, 1) * 20
]

Oscillation

Shrimply provides math functions directly instead of through JavaScript’s Math object:

After EffectsShrimply

value + Math.sin(time * 4) * 20

Remapping values

Use lerp with a clamped progress value in place of After Effects’ linear function. This moves from 0 to 100 over two seconds:

After EffectsShrimply

linear(time, 0, 2, 0, 100)

Conditions

Rhai uses if blocks instead of JavaScript’s ? : conditional operator:

After EffectsShrimply

time < 1 ? 0 : 100

Adobe-specific features

Shrimply does not provide After Effects objects such as thisComp, thisLayer, or property links. It also does not expose keyframes to expressions, so loopIn(), loopOut(), and valueAtTime() have no direct equivalent. To loop an item’s playback, open Playback ‣ Repeat in the inspector and set Strategy to Repeat or Ping Pong. Rewrite other expressions using only the values and functions in Expression basics.