@feugene/mu/src/is/isFunction.ts

Helpful TS utilities without dependencies

const symToStringTag = Symbol.toStringTag

const asyncTag = '[object AsyncFunction]',
  funcTag = '[object Function]',
  genTag = '[object GeneratorFunction]',
  nullTag = '[object Null]',
  proxyTag = '[object Proxy]',
  undefinedTag = '[object Undefined]'

/**
 * This function evaluates whether all parameters are function
 */
export function isFunctions(...parameters: any[]): boolean {
  if (parameters.length === 0) {
    throw new Error('Please provide at least one number to evaluate isInteger.')
  }

  const invalid = parameters.some(parameter => !isFunction(parameter))

  return !invalid
}

export default function isFunction(parameter: any): boolean {
  const tag = baseGetTag(parameter)
  return tag === funcTag || tag === genTag || tag === asyncTag || tag === proxyTag
}

/**
 * The base implementation of `getTag` without fallbacks for buggy environments.
 *
 * @private
 */
function baseGetTag(value: any): string {
  if (value == null) {
    return value === undefined ? undefinedTag : nullTag
  }
  return symToStringTag in new Object(value) ? getRawTag(value) : objectToString(value)
}

/**
 * A specialized version of `baseGetTag` which ignores `Symbol.toStringTag` values.
 *
 * @private
 */
function getRawTag(value: any): string {
  const isOwn = Object.prototype.hasOwnProperty.call(value, symToStringTag)
  const tag = value[symToStringTag]

  let unmasked = false

  try {
    value[symToStringTag] = undefined
    unmasked = true
  } catch (error) {}

  const result = objectToString(value)
  if (unmasked) {
    if (isOwn) {
      value[symToStringTag] = tag
    } else {
      delete value[symToStringTag]
    }
  }
  return result
}

/**
 * @private
 */
function objectToString(value: any): string {
  return Object.prototype.toString.call(value)
}