Typescript Glossary


An animation being executed by the frameloop. Normally found attached to a SpringValue.

class Animation<T = any> {
changed: boolean
values: readonly AnimatedValue[]
toValues: readonly number[] | null
fromValues: readonly number[]
to: T | FluidValue<T>
from: T | FluidValue<T>
config: AnimationConfig
immediate: boolean


Most of the reserved animation props, except to, from, loop, and the event props.

interface AnimationProps<T = any> {
config?: SpringConfig | ((key: StringKeys<T>) => SpringConfig)
delay?: number | ((key: StringKeys<T>) => number)
immediate?: MatchProp<T>
cancel?: MatchProp<T>
pause?: MatchProp<T>
reset?: MatchProp<T>
reverse?: boolean
default?: boolean | SpringProps<T>


A value that any SpringValue or Controller can animate to.

export declare type ControllerUpdate< State extends Lookup = Lookup, Item = undefined, > = unknown & ToProps<State> & ControllerProps<State, Item>


Lookup is typically inferred, so you probably won't need to use it. It's primarily used to infer the animatable properties from our hooks, e.g. opacity

interface Lookup<T = any> {
[key: string]: T


export type OneOrMore<T> = T | readonly T[]


The props of a useSpring call or its async update function. The T parameter can be a set of animated values (as an object type) or a primitive type for a single animated value.

type SpringUpdate<T = any> = ToProps<T> & SpringProps<T>
type SpringsUpdate<State extends Lookup = UnknownProps> =
| OneOrMore<ControllerUpdate<State>>
| ((index: number, ctrl: Controller<State>) => ControllerUpdate<State> | null)


SpringValues is contextual to the values you pass to your hook e.g. opacity. It's type signature is quite complicated, so it's easier to show how you use it.

type MySpringValues = SpringValues<{
opacity: number
y: string


TransitionState is the internal state attached to a particular Item (a single datum from the data array you pass).

interface TransitionState<Item = any, State extends Lookup = Lookup> {
key: any
item: Item
ctrl: Controller<State>
phase: TransitionPhase
expired?: boolean
expirationId?: number


Intersected with other object types to allow for unknown properties.

export interface UnknownProps extends Lookup<unknown> {}