# Receivers and Deferred Calls > UForm for JavaScript The same verbs run on the calling thread with no receiver, and block on an executor through `on`: ```javascript const here = model.textEncode(["a small red panda"], arena); const there = model.on(executor).textEncode(["a small red panda"], arena); ``` `import * as uform from 'uform';` `import { ModelOn } from 'uform';` `import { ModelDeferredOn } from 'uform';` `import { TrainerDeferredOn } from 'uform';` `import { Deferred } from 'uform';` ## ProgressCallback Hears a long call's advance; answering `false` stops it with `cancelled`. ```typescript type ProgressCallback = (completed: number, total: number) => boolean | void ``` ## Mood What an executor does with its threads or streams once it goes idle. ```typescript enum Mood ``` - `Parked` = `"parked"`: Idle threads sleep; the next call pays a wake-up. - `Spinning` = `"spinning"`: Idle threads stay hot, trading power for the next call's latency. ## Answer How a receiver hands back what its verbs answer: as is, or as a [`Deferred`](https://www.unum.cloud/docs/uform/javascript/errors.md#Deferred) of it. ```typescript type Answer = Receiving extends "deferred" ? Deferred : Answered ``` ## ModelOn The verbs of one model, blocking on one executor: `model.on(executor)`. ```typescript class ModelOn extends ModelVerbs<"blocking"> ``` Every call starts after every earlier submission to that executor, and returns with its outputs written. ## ModelOn Made by `model.on(executor)`, never directly. ```typescript new ModelOn( compiled: CompiledModel, executor: Executor | undefined, ) ``` ## * Reports the model's geometry and placement in one call. ```typescript describe(): Answer ``` Calls `uform_model_describe`. ## text* Encodes texts through one forward; every UTF-8 byte is a token. ```typescript textEncode( texts: readonly (string | Uint8Array)[] | Tape, arena: Arena, config: EncodeConfig = {}, ): Answer ``` Calls `uform_text_encode`. - `texts`: Strings, UTF-8 bytes already encoded, or a tape of them. - `arena`: The memory the outputs land in, rewound by the call. - `config`: The surfaces, their scalar, and a progress handler. ## text* Scores each item's legal choices through one forward, a softmax over them alone at the item's group's calibrated inverse temperature; a model without the byte decoder reports `unsupported`. ```typescript textChoose( texts: readonly (string | Uint8Array)[] | Tape, choices: readonly (string | Uint8Array)[] | Tape, arena: Arena, config: ChooseConfig = {}, ): Answer ``` Calls `uform_text_choose`. - `texts`: The states, each ending where its choice goes. - `choices`: Each item's legal choices, one byte each, like "yn". - `arena`: The memory the probabilities land in, rewound by the call. - `config`: The question types and a progress handler. ## image* Decodes and encodes JPEG, PNG or WebP files; the browser build reports `unsupported`. ```typescript imageEncode( images: readonly Uint8Array[] | Tape, arena: Arena, config: EncodeConfig = {}, ): Answer ``` Calls `uform_image_encode`. - `images`: One encoded file per item, or a tape of them. - `arena`: The memory the outputs land in, rewound by the call. - `config`: The surfaces, their scalar, and a progress handler. ## imageEncode* Encodes decoded images, resized on the executor's side. ```typescript imageEncodePixels( images: readonly Pixels[], arena: Arena, config: EncodeConfig = {}, ): Answer ``` Calls `uform_image_encode_pixels`. - `images`: `ImageData`, or RGB or RGBA bytes with their width and height. - `arena`: The memory the outputs land in, rewound by the call. - `config`: The surfaces, their scalar, and a progress handler. ## video* Decodes and encodes MP4 or WebM clips; the browser build reports `unsupported`. ```typescript videoEncode( videos: readonly Uint8Array[] | Tape, arena: Arena, config: EncodeConfig = {}, ): Answer ``` Calls `uform_video_encode`. - `videos`: One encoded file per item, or a tape of them. - `arena`: The memory the outputs land in, rewound by the call. - `config`: The surfaces, their scalar, and a progress handler. ## audio* Decodes and encodes WAV, FLAC, MP3 or Opus files; the browser build reports `unsupported`. ```typescript audioEncode( recordings: readonly Uint8Array[] | Tape, arena: Arena, config: EncodeConfig = {}, ): Answer ``` Calls `uform_audio_encode`. - `recordings`: One encoded file per item, or a tape of them. - `arena`: The memory the outputs land in, rewound by the call. - `config`: The surfaces, their scalar, and a progress handler. ## audioEncode* Encodes decoded mono recordings, resampled to the model's rate where `sampleRate` differs. ```typescript audioEncodeSamples( recordings: readonly Float32Array[] | Tape, sampleRate: number, arena: Arena, config: EncodeConfig = {}, ): Answer ``` Calls `uform_audio_encode_samples`. - `recordings`: One run of samples per item, or a tape of them. - `sampleRate`: Samples per second shared by every recording. - `arena`: The memory the outputs land in, rewound by the call. - `config`: The surfaces, their scalar, and a progress handler. ## executor The executor the verbs run on; absent runs them on the calling thread. ```typescript readonly executor: Executor | undefined ``` ## ModelDeferredOn The verbs of one model, submitted to one executor and answered as [`Deferred`](https://www.unum.cloud/docs/uform/javascript/errors.md#Deferred) calls: `model.deferred(executor)`. ```typescript class ModelDeferredOn extends ModelVerbs<"deferred"> ``` A verb borrows its arena until final, and waits into the same views a blocking call answers. ## ModelDeferredOn Made by `model.deferred(executor)`, never directly. ```typescript new ModelDeferredOn(compiled: CompiledModel, executor: Executor) ``` ## executor The executor the verbs run on; absent runs them on the calling thread. ```typescript readonly executor: Executor | undefined ``` ## TrainerDeferredOn The trainer's verbs, submitted to its executor and answered as Deferred (`*`) calls: `trainer.deferred()`. ```typescript class TrainerDeferredOn extends TrainerVerbs<"deferred"> ``` ## TrainerDeferredOn Made by `trainer.deferred()`, never directly. ```typescript new TrainerDeferredOn( compiled: CompiledTrainer, executor: Executor, ) ``` ## step Applies one optimizer step over this process's items and every peer's. ```typescript step( batch: TrainerBatch, config: TrainerStepConfig = {}, ): Answer ``` Calls `uform_trainer_step`. - `batch`: This process's items, their modalities, bags and relations. - `config`: Where the scored embeddings land. ## save Writes the weights and the step as a safetensors checkpoint; only process zero writes. ```typescript save(path: string): Answer ``` Calls `uform_trainer_save`. - `path`: The destination, written whole and renamed into place. ## Deferred A call submitted by a deferred receiver, final once its executor finishes it. ```typescript class Deferred implements PromiseLike, Disposable ``` It keeps everything the library reads or writes alive until then - the outcome, the inputs, the outputs and every handle it names - so none of them is collected under the call. [`status`](#status) polls without blocking, [`wait`](#wait) blocks and answers, and `await` runs that wait on the libuv pool; both answer the same cached result, or throw the same failure, however often they are asked. On the WebAssembly backend the call is final once submitted. ``` const encoded = await call; // or: call.wait() ``` ## Deferred Made by a verb of a deferred receiver, never directly. ```typescript new Deferred(call: CompiledDeferred, answer: (raw: never) => T) ``` ## wait Blocks the calling thread until the call is final, then answers its result or throws its failure. ```typescript wait(): T ``` Calls `uform_outcome_wait`. ## then Waits off the calling thread, which is what `await` reaches for. ```typescript then( onFulfilled?: ((value: T) => Fulfilled | PromiseLike) | null, onRejected?: ((reason: unknown) => Rejected | PromiseLike) | null, ): Promise ``` Calls `uform_outcome_wait` on the libuv pool. ## status [`Status.Deferred`](https://www.unum.cloud/docs/uform/javascript/errors.md#Deferred) until the call is final, then [`Status.Success`](https://www.unum.cloud/docs/uform/javascript/errors.md#Success) or its failure. ```typescript readonly status: Status ``` Calls `uform_outcome_status`.