Utilities

Low-level helpers used by the hooks. Safe to call from your own file pickers if you are not using useDropzone.

import { isFileAccepted, acceptPatternsToInputAccept, validateFiles } from 'react-upload-kit';

isFileAccepted

function isFileAccepted(
  file: Pick<File, 'name' | 'type'>,
  accept: AcceptPattern[] | undefined,
): boolean

Returns true if accept is empty/undefined, or if any pattern matches.

• .pdf — filename suffix, case-insensitive
• image/* — MIME group
• image/png — exact MIME

acceptPatternsToInputAccept

function acceptPatternsToInputAccept(
  accept: AcceptPattern[] | undefined,
): string | undefined

Joins patterns with commas for <input accept="…">. Returns undefined when there is nothing to set.

validateFiles

function validateFiles(
  files: File[],
  config: {
    accept?: AcceptPattern[];
    maxFileSize?: number;
    minFileSize?: number;
    maxFiles?: number;
    validator?: FileValidator;
  },
  existingFileCount?: number,
): { accepted: File[]; rejected: FileRejection[] }

existingFileCount (default 0) is how many files are already tracked. useUploader passes files.length so maxFiles is global. A standalone picker should pass the same number if it shares that cap.

A file is rejected if it has any error. Custom validator errors are appended after built-in checks; a file can have several errors at once.