const promise = new Promise((resolve, reject) => {
reject("error");
resolve("success2");
});
promise
.then(res => {
console.log("then1: ", res);
}).then(res => {
console.log("then2: ", res);
}).catch(err => {
console.log("catch: ", err);
}).then(res => {
console.log("then3: ", res);
})
解析
catch不管被连接到哪里，都能捕获上层未捕捉过的错误。
至于then3也会被执行，那是因为catch()也会返回一个Promise，且由于这个Promise没有返回值，所以打印出来的是undefined。
结果
"catch: " "error"
"then3: " undefined
