当 AbortSignal 被触发时指定的可选原因。
AbortSignal
🌐 An optional reason specified when the AbortSignal was triggered.
const ac = new AbortController(); ac.abort(new Error('boom!')); console.log(ac.signal.reason); // Error: boom! 拷贝
const ac = new AbortController(); ac.abort(new Error('boom!')); console.log(ac.signal.reason); // Error: boom!