IsConstructor.js

'use strict';

var GetIntrinsic = require('../GetIntrinsic.js');

var $construct = GetIntrinsic('%Reflect.construct%', true);

var DefinePropertyOrThrow = require('./DefinePropertyOrThrow');
try {
	DefinePropertyOrThrow({}, '', { '[[Get]]': function () {} });
} catch (e) {
	// Accessor properties aren't supported
	DefinePropertyOrThrow = null;
}

// https://ecma-international.org/ecma-262/6.0/#sec-isconstructor

if (DefinePropertyOrThrow && $construct) {
	var isConstructorMarker = {};
	var badArrayLike = {};
	DefinePropertyOrThrow(badArrayLike, 'length', {
		'[[Get]]': function () {
			throw isConstructorMarker;
		},
		'[[Enumerable]]': true
	});

	module.exports = function IsConstructor(argument) {
		try {
			// `Reflect.construct` invokes `IsConstructor(target)` before `Get(args, 'length')`:
			$construct(argument, badArrayLike);
		} catch (err) {
			return err === isConstructorMarker;
		}
	};
} else {
	module.exports = function IsConstructor(argument) {
		// unfortunately there's no way to truly check this without try/catch `new argument` in old environments
		return typeof argument === 'function' && !!argument.prototype;
	};
}