Validation

Validation runs client-side before a file enters the upload queue. A file that fails validation moves immediately to failed and never reaches the adapter. The library ships several built-in validators and a composeValidators helper for combining them.

Built-in validators

Validator	Platform	Description
maxFileSize(bytes)	Both	Checks file.size
allowedTypes(types)	Both	Checks file.type against MIME types (supports wildcards like video/*)
maxDuration(seconds)	Both	Web: DOM video element. Native: expo-video-metadata (optional, skips if missing)

Composing validators

Use composeValidators to chain validators in order. Stops at the first failure.

import {
  composeValidators,
  maxFileSize,
  allowedTypes,
  maxDuration,
} from "@hyperserve/upload";

const validate = composeValidators(
  maxFileSize(500 * 1024 * 1024),     // 500 MB
  allowedTypes(["video/*"]),           // any video MIME type
  maxDuration(120),                    // 2 minutes
);

Pass the result to your config:

import { createHyperserveConfig } from "@hyperserve/upload-adapter-hyperserve";

const config = createHyperserveConfig({
  // ...
  validate,
});

Custom validators

A validator is any function matching the Validator type:

type Validator = (file: FileRef) => ValidationResult | Promise<ValidationResult>;

type ValidationResult =
  | { valid: true }
  | { valid: false; reason: string };

Example: minimum file size

const minFileSize = (bytes: number): Validator => (file) => {
  if (file.size < bytes) {
    return { valid: false, reason: `File must be at least ${bytes} bytes` };
  }
  return { valid: true };
};

Compose custom validators alongside built-in ones:

const validate = composeValidators(
  minFileSize(1024),
  maxFileSize(500 * 1024 * 1024),
  allowedTypes(["video/mp4", "video/webm"]),
);