index.js

/**
 * lodash 3.9.0 (Custom Build) <https://lodash.com/>
 * Build: `lodash modern modularize exports="npm" -o ./`
 * Copyright 2012-2015 The Dojo Foundation <http://dojofoundation.org/>
 * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
 * Copyright 2009-2015 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 * Available under MIT license <https://lodash.com/license>
 */

/** `Object#toString` result references. */
var funcTag = '[object Function]';

/**
 * Used to match `RegExp` [special characters](http://www.regular-expressions.info/characters.html#special).
 * In addition to special characters the forward slash is escaped to allow for
 * easier `eval` use and `Function` compilation.
 */
var reRegExpChars = /[.*+?^${}()|[\]\/\\]/g,
    reHasRegExpChars = RegExp(reRegExpChars.source);

/** Used to detect host constructors (Safari > 5). */
var reIsHostCtor = /^\[object .+?Constructor\]$/;

/**
 * Converts `value` to a string if it's not one. An empty string is returned
 * for `null` or `undefined` values.
 *
 * @private
 * @param {*} value The value to process.
 * @returns {string} Returns the string.
 */
function baseToString(value) {
  if (typeof value == 'string') {
    return value;
  }
  return value == null ? '' : (value + '');
}

/**
 * Checks if `value` is object-like.
 *
 * @private
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is object-like, else `false`.
 */
function isObjectLike(value) {
  return !!value && typeof value == 'object';
}

/** Used for native method references. */
var objectProto = Object.prototype;

/** Used to resolve the decompiled source of functions. */
var fnToString = Function.prototype.toString;

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

/**
 * Used to resolve the [`toStringTag`](https://people.mozilla.org/~jorendorff/es6-draft.html#sec-object.prototype.tostring)
 * of values.
 */
var objToString = objectProto.toString;

/** Used to detect if a method is native. */
var reIsNative = RegExp('^' +
  escapeRegExp(fnToString.call(hasOwnProperty))
  .replace(/hasOwnProperty|(function).*?(?=\\\()| for .+?(?=\\\])/g, '$1.*?') + '$'
);

/**
 * Gets the native function at `key` of `object`.
 *
 * @private
 * @param {Object} object The object to query.
 * @param {string} key The key of the method to get.
 * @returns {*} Returns the function if it's native, else `undefined`.
 */
function getNative(object, key) {
  var value = object == null ? undefined : object[key];
  return isNative(value) ? value : undefined;
}

/**
 * Checks if `value` is a native function.
 *
 * @static
 * @memberOf _
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a native function, else `false`.
 * @example
 *
 * _.isNative(Array.prototype.push);
 * // => true
 *
 * _.isNative(_);
 * // => false
 */
function isNative(value) {
  if (value == null) {
    return false;
  }
  if (objToString.call(value) == funcTag) {
    return reIsNative.test(fnToString.call(value));
  }
  return isObjectLike(value) && reIsHostCtor.test(value);
}

/**
 * Escapes the `RegExp` special characters "\", "/", "^", "$", ".", "|", "?",
 * "*", "+", "(", ")", "[", "]", "{" and "}" in `string`.
 *
 * @static
 * @memberOf _
 * @category String
 * @param {string} [string=''] The string to escape.
 * @returns {string} Returns the escaped string.
 * @example
 *
 * _.escapeRegExp('[lodash](https://lodash.com/)');
 * // => '\[lodash\]\(https:\/\/lodash\.com\/\)'
 */
function escapeRegExp(string) {
  string = baseToString(string);
  return (string && reHasRegExpChars.test(string))
    ? string.replace(reRegExpChars, '\\$&')
    : string;
}

module.exports = getNative;