小编MWY*_*MWY的帖子

我对承诺感到困惑！

我使用Promise then而不返回，如下所示：

new Promise((resolve, reject) => {
    resolve("1");
}).then((v1) => {
    console.log("v1");
    new Promise((resolve, reject) => {
        //Time-consuming operation, for example: get data from database;
        setTimeout(() => {
            resolve(2)
        }, 3000);
    }).then((v11) => {
        console.log("v11");
    })
}).then((v2) => {
    console.log("v2")
});

我得到这个结果v1 v2 v11。然后，我用另一种写法，如下所示：

 new Promise((resolve, reject) => {
    resolve("1");
}).then((v1) => {
    console.log("v1");
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve(2)
        }, 3000)
    }).then((v11) => {
        console.log("v11");
    })
}).then((v2) => {
    console.log("v2") …