isNative.js

var escapeRegExp = require('../string/escapeRegExp'),
    isObjectLike = require('../internal/isObjectLike');

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

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

/** 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, '$1.*?') + '$'
);

/**
 * 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);
}

module.exports = isNative;