Using Chained Promise.allSettled-CodePudding

For a quick rundown of what I'm trying to do. I've got a basic for loop that generates an array of IPs that I want to fetch, I want to check that the response.status is 200 (Which I haven't implemented yet) and then take the IPs that returned a status of 200 and only keep those IPs. I tried doing this with Promise.all but was left with the problem of it rejecting one, thus rejecting all of them. So now I'm at this code.

async function example() {
    var arr = [];
    for (let i = 4; i <= 255; i  ) {
        var ip = 'http://172.16.238.'   i.toString()   ':443';
        arr.push(ip);
    }
    Promise.allSettled(arr.map(u=>fetch(u))).then(responses => Promise.allSettled(responses.map(res => res.text()))).then(texts => {fetch('https://testing.com', {method: 'POST', body: texts})})
}
example()

I'm getting res.text() isn't a function when used with allSettled. But I'm also confused as to how I would approach checking the status of each response, I'm mapping the url to each fetch and then mapping a response to it's text, so would I do the status check in the second mapping? The mapping is a bit confusing to me.

Any explanation would be great, thanks

CodePudding user response：

allSettled does not return an array with the resolved values - rather, it returns an array of objects, where the objects contain status / value / reason properties. To get to the resolve value, if there is one, access the .value property.

But a single allSettled will do - call .text inside the first callback if it hasn't errored.

function example() {
    var arr = [];
    for (let i = 4; i <= 255; i  ) {
        var ip = 'http://172.16.238.'   i.toString()   ':443';
        arr.push(ip);
    }
    Promise.allSettled(arr.map(
        u => fetch(u)
            .then(res => { if (res.ok) return res.text(); })
    ))
        .then(results => {
            const texts = results
                .filter(result => result.status === 'fulfilled' && result.value)
                .map(result => result.value);
            fetch('https://testing.com', { method: 'POST', body: texts })
                // ...
        })
}