lodash/internal/isBindable.js

import baseSetData from './baseSetData';
import isNative from '../lang/isNative';
import support from '../support';

/** Used to detect named functions. */
var reFuncName = /^\s*function[ \n\r\t]+\w/;

/** Used to detect functions containing a `this` reference. */
var reThis = /\bthis\b/;

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

/**
 * Checks if `func` is eligible for `this` binding.
 *
 * @private
 * @param {Function} func The function to check.
 * @returns {boolean} Returns `true` if `func` is eligible, else `false`.
 */
function isBindable(func) {
  var result = !(support.funcNames ? func.name : support.funcDecomp);

  if (!result) {
    var source = fnToString.call(func);
    if (!support.funcNames) {
      result = !reFuncName.test(source);
    }
    if (!result) {
      // Check if `func` references the `this` keyword and store the result.
      result = reThis.test(source) || isNative(func);
      baseSetData(func, result);
    }
  }
  return result;
}

export default isBindable;