instanceof
运算符不适用于Error
子类的实例。为什么会这样?相同的代码在浏览器中运行良好,请尝试我的fiddle进行示例。
以下代码在浏览器中输出true
,但在babel-node下是false:
class Sub extends Error {
}
let s = new Sub()
console.log(`The variable 's' is an instance of Sub: ${s instanceof Sub}`)
我能想象这只能归咎于babel-node中的一个错误,因为
instanceof
对于除Error
之外的其他基类有效。
.babelrc
{
"presets": ["es2015"]
}
编译输出
这是由Babel 6.1.18编译的JavaScript代码:
'use strict';
function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }
function _possibleConstructorReturn(self, call) { if (!self) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return call && (typeof call === "object" || typeof call === "function") ? call : self; }
function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function, not " + typeof superClass); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }
var Sub = (function (_Error) {
_inherits(Sub, _Error);
function Sub() {
_classCallCheck(this, Sub);
return _possibleConstructorReturn(this, Object.getPrototypeOf(Sub).apply(this, arguments));
}
return Sub;
})(Error);
var s = new Sub();
console.log('The variable \'s\' is an instance of Sub: ' + (s instanceof Sub));