类：ReferenceError

🌐 Class: ReferenceError

• 扩展：<errors.Error>

表示正在尝试访问一个未定义的变量。这类错误通常表示代码中有拼写错误，或者程序本身存在其他问题。

🌐 Indicates that an attempt is being made to access a variable that is not defined. Such errors commonly indicate typos in code, or an otherwise broken program.

虽然客户端代码可能会生成并传播这些错误，但在实际操作中，只有 V8 会这样做。

🌐 While client code may generate and propagate these errors, in practice, only V8 will do so.

doesNotExist;
// Throws ReferenceError, doesNotExist is not a variable in this program. 拷贝

除非应用正在动态生成和运行代码，否则 ReferenceError 实例表示代码或其依赖中存在错误。

🌐 Unless an application is dynamically generating and running code, ReferenceError instances indicate a bug in the code or its dependencies.