运行以下代码时,我会得到不同的结果,具体取决于我是否注释掉了console.log(“fnError：”,fnError).这对我来说似乎很不对劲.
世界上如何调用console.log影响我的承诺？
function run() {
var fn = function(){
throw new Error("incorrect message");
};
// returns a promise that should fail with
// an error object whose .message is "correct message"
var promisifiedFn = function(){
return Promise.resolve()
.then(fn)
.catch((fnError) => {
// commenting this out fixes things! //
console.log("fnError: ",fnError);
///////////////////////////////////////
fnError.message = "correct message";
throw fnError;
})
}
promisifiedFn().catch((e) => {
console.log("caught error.message:",e.message);
console.log("caught error:",e);
});
}
run();
以上产生：
// fnError: Error: incorrect message
// at fn (/Users/sam/dev/ethereum/pennyeth/js/temp.js:18:9)
// at 注意记录“不正确的消息”.如果你注释掉console.log(“fnError：”,fnError),你会得到：
// caught error.message: correct message
// caught error: Error: correct message
// at fn (/Users/sam/dev/ethereum/pennyeth/js/temp.js:18:9)
// at 运行节点8.0.0
最佳答案
这是预期的行为.
记录错误(至少通过util.inspect或String)会评估其.stack属性.实例化错误对象时,不会初始化堆栈字符串,但是为了节省内存而延迟构建堆栈字符串.堆栈跟踪将包含错误消息,当您更改.message属性时,它将反映或不反映在堆栈跟踪中,具体取决于是否已创建.
从the V8 stack trace API description开始：
For efficiency stack traces are not formatted when they are captured but on demand,the first time the stack property is accessed.
从the official node Error documentation开始：
The string representing the stack trace is lazily generated when the error.stack property is accessed.
