javascript-违反promise.all

我有一个承诺实现,如MDN上的实现：

    var p1 = new Promise((resolve, reject) => {
        setTimeout(resolve, 1000, "one");
    });
    var p2 = new Promise((resolve, reject) => {
        setTimeout(resolve, 2000, "two");
    });
    var p3 = new Promise((resolve, reject) => {
        setTimeout(resolve, 3000, "three");
    });
    var p4 = new Promise((resolve, reject) => {
        setTimeout(resolve, 4000, "four");
    });
    var p5 = new Promise((resolve, reject) => {
        reject("reject");
    });
    
    Promise.all([p1, p2, p3, p4, p5]).then(value => {
        console.log(value);
    }, function(reason) {
        console.log(reason)
    });

这样可以快速捕获错误：

Promise.all is rejected if one of the elements is rejected and Promise.all fails fast: If you have four promises which resolve after a timeout, and one calls reject immediately, then Promise.all rejects immediately.

但是,promise中的功能不会停止运行.我想要的是,如果一个功能拒绝,其他功能将停止运行(防止向用户发送无用的消息).

在拒绝之后继续运行的承诺示例：

var p1 = new Promise((resolve, reject) => {
    setTimeout(resolve, 1000, "one");
});
var p2 = new Promise((resolve, reject) => {
    setTimeout(resolve, 2000, "two");
});
var p3 = new Promise((resolve, reject) => {
    setTimeout(resolve, 3000, "three");
});
var p4 = new Promise((resolve, reject) => {
    setTimeout(() => {
        console.log('Don\'t show this after a reject!');
        resolve();
    }, 4000);
});
var p5 = new Promise((resolve, reject) => {
    reject("reject");
});

Promise.all([p1, p2, p3, p4, p5]).then(value => {
    console.log(value);
}, function(reason) {
    console.log(reason)
});

解决方法:

因为停止其他动作是特定于动作的,而不是通用的,所以诺言中没有什么可以做到的.例如,在您的示例中,必须保留计时器句柄,然后使用clearTimeout.对于ajax请求,您可能需要执行中止调用；还有其他的东西.

因此,您需要在实际代码中以特定于实际代码的方式处理此问题,对Promise.all(或您所拥有的第二个arg)返回的promise使用.catch.

在您问题的特定代码中,它看起来像这样(我将输出也添加到了我们也不会取消的计时器中),但是它又会根据您要取消的内容而有所不同：

var timersToReject = [];
var p1 = new Promise((resolve, reject) => {
    setTimeout(v => {
        console.log("resolving " + v);
        resolve(v);
    }, 1000, "one");
});
var p2 = new Promise((resolve, reject) => {
    setTimeout(v => {
        console.log("resolving " + v);
        resolve(v);
    }, 2000, "two");
});
var p3 = new Promise((resolve, reject) => {
    setTimeout(v => {
        console.log("resolving " + v);
        resolve(v);
    }, 3000, "three");
});
var p4 = new Promise((resolve, reject) => {
    timersToReject.push(setTimeout(() => {
        console.log('Don\'t show this after a reject!');
        resolve();
    }, 4000));
});
var p5 = new Promise((resolve, reject) => {
    reject("reject");
});

Promise.all([p1, p2, p3, p4, p5]).then(value => {
    console.log(value);
}, function(reason) {
    console.log(reason)
    timersToReject.forEach(t => clearTimeout(t));
});