@feugene/mu/src/internal/arrayLikeKeys.ts

Helpful TS utilities without dependencies

import isArguments from '~/is/isArguments'
import isBuffer from '~/is/isBuffer'
import isTypedArray from '~/is/isTypedArray'

import times from '~/utils/times'
import isIndex from './isIndex'

/** Used for built-in method references. */
const objectProto = Object.prototype

/** Used to check objects for own properties. */
const hasOwnProperty = objectProto.hasOwnProperty

/**
 * Creates an array of the enumerable property names of the array-like `value`.
 *
 * @private
 * @param {*} value The value to query.
 * @param {boolean} inherited Specify returning inherited property names.
 * @returns {Array|[]} Returns the array of property names.
 */
export default function arrayLikeKeys(value: any, inherited: boolean = false): string[] {
  const isArray_ = Array.isArray(value),
    isArgument = !isArray_ && isArguments(value),
    isBuff = !isArray_ && !isArgument && isBuffer(value),
    isType = !isArray_ && !isArgument && !isBuff && isTypedArray(value),
    skipIndexes = isArray_ || isArgument || isBuff || isType,
    result = skipIndexes ? (times(value.length, String) as string[]) : [],
    length = result.length

  for (const key in value) {
    if (
      (inherited || hasOwnProperty.call(value, key)) &&
      !(
        skipIndexes &&
        // Safari 9 has enumerable `arguments.length` in strict mode.
        (key === 'length' ||
          // Node.js 0.10 has enumerable non-index properties on buffers.
          (isBuff && (key === 'offset' || key === 'parent')) ||
          // PhantomJS 2 has enumerable non-index properties on typed arrays.
          (isType && (key === 'buffer' || key === 'byteLength' || key === 'byteOffset')) ||
          // Skip index properties.
          isIndex(key, length))
      )
    ) {
      result.push(key)
    }
  }

  return result
}