when.ts

when.ts

import { Accessor } from 'solid-js'

export function when<
  TAccessors extends Array<Accessor<any>>,
  const TValues extends { [TKey in keyof TAccessors]: Exclude<ReturnType<TAccessors[TKey]>, null | undefined | false> }
>(...accessors: TAccessors) {
  function callback<const TResult>(): TValues | undefined
  function callback<const TResult>(callback: (...values: TValues) => TResult): TResult | undefined
  function callback<const TResult>(callback?: (...values: TValues) => TResult) {
    const values = new Array(accessors.length)

    for (let i = 0; i < accessors.length; i++) {
      const _value = accessors[i]()
      if (_value === undefined || _value === null || _value === false) return undefined
      values[i] = _value
    }

    return callback ? callback(...(values as any)) : values
  }
  return callback
}