用promise.all处理错误

Question

Promise.all(
    [[getNetworkstuff(url1)],[getNetworkstuff(url2)]]
    //please note that the arrays within the array are larger in my application
    //otherwise I would just use one big array not arrays in arrays
)
.then(function(result){//Stuff worked})
.catch(function(err){//Stuff broke});

function getNetworkstuff(url){
    return new Promise(function(resolve,reject){//here will be awesome network code})
}

我可以看到promise没有实现，因为返回的result数组包含适当的拒绝promise。

[[PromiseStatus]]: "rejected"
[[PromiseValue]]: Error: HTTP GET resulted in HTTP status code 404.

有人能告诉我为什么不调用catch吗？（如果我在promise.all()中有一个promise数组，其中一个被拒绝，我就知道是这样）

Answer 1

看看你的控制台

function getNetworkstuff(url) {
    return new Promise(function(resolve, reject) {
        setTimeout(function() {
            console.log('resolving', url);
            resolve(url);
        }, 5000);
    });
}
Promise.all([[getNetworkstuff('url1')],[getNetworkstuff('url2')]])
.then(function(result){
    console.log('It worked', result);
})
.catch(function(err){
    console.log('It failed', result);
});

注意，它在解析任何内容之前5秒输出“it Worked”

Promise.all([getNetworkstuff('url1'), getNetworkstuff('url2')])
.then(function(result){
    console.log('It worked', result);
})
.catch(function(err){
    console.log('It failed', result);
});

现在比较一下没有数组的数组-注意在这两种情况下It Worked旁边记录的内容的不同

function getNetworkstuff(url) {
    return new Promise(function(resolve, reject) {
        if(url == 'url1') {
            setTimeout(function() {
                console.log('resolving', url);
                resolve(url);
            }, 5000);
        }
        else {
            console.log('rejecting', url);
            reject(url);
        }
    });
}

Promise.all([getNetworkstuff('url1'), getNetworkstuff('url2')])
.then(function(result){
    console.log('It worked', result);
})
.catch(function(err){
    console.log('It failed', result);
});

function fn(s) {
    return s.toUpperCase();
}
function fn2(arr) {
    console.log(arr); // [["A"], ["B"]]
}
fn2([[fn('a')],[fn('b')]]);