javascript - 拒绝处理不开火

Question

我正在尝试使用 rejectionhandled 但我无法启动它。下面的代码应该基于我能找到的所有文档工作。我为 rejectionhandled 注册了一个监听器，然后拒绝一个 promise 并捕获它。在启用标志的 chrome 和 firefox 中，“测试”会被记录但不会被“拒绝”。我错过了什么？

window.addEventListener("rejectionhandled", e => console.log("rejected"), false);
new Promise((resolve, reject) => setTimeout(reject, 1000)).catch(err => console.error("testing"))

Answer 1

rejectionhandled event不会在每次处理的拒绝时触发，它只会在最初未处理的拒绝时触发(导致 unhandledrejection events )但后来确实附加了处理程序。

事件是从 implementation-defined HostPromiseRejectionTracker 的 HTML 实现中触发的在 ECMAScript 规范中，其说明是

HostPromiseRejectionTracker is called in two scenarios:

• When a promise is rejected without any handlers, it is called with its operation argument set to "reject".
• When a handler is added to a rejected promise for the first time, it is called with its operation argument set to "handle".