如何从数组异步写入 JSON 文件？

Question

I'm scraping some data and pushing it to any array from which it is written to a JSON file. Currently it writes to the JSON file after every push to th array...

    const myArray = [];
    const htmlString = await rp(url);
    $('a','#atozindex', htmlString).map(async (index, element) => {
        let link = $(element).attr('href');
        if (link) {
            //Do something
            myArray.push({ item1, item2, item3 });
            fs.writeFile("./arrayContents.json", JSON.stringify(myArray), function(err) {
                if(err) {
                    console.log(err);
                }
                console.log("Some Message");
            });
        }
    });
    return myArray;

I want to have it push only once at the very end when all the data is already in the array. So something like this:

    const myArray = [];
    const htmlString = await rp(url);
    $('a','#atozindex', htmlString).map(async (index, element) => {
        let link = $(element).attr('href');
        if (link) {
            //Do something
            myArray.push({ item1, item2, item3 });
        }
    });
    fs.writeFile("./arrayContents.json", JSON.stringify(myArray), function(err) {
        if(err) {
            console.log(err);
        }
        console.log("Some Message");
    return myArray;

But I'm having some trouble figuring it out.

Answer 1

i think that you can do that like this

$.when(mapping()).then(function( ) { // mapping is a function for your map and until it finish then do that ...

});

OR

$.when(mapping()).done(function( ) { // mapping is a function for your map and until it finish then do that ...

    });

until map finish then or done do somting , thant's it

you can see learn more about when/then or done here

Answer 2

My async/await is rusty, to be sure to test... but I think you have 2 options - await all the asyncs:

const myArray = [];
const htmlString = await rp(url);
$('a','#atozindex', htmlString).map(async (index, element) => {
    let link = $(element).attr('href');
    if (link) {
        //Do something
        myArray.push({ item1, item2, item3 });
    }
}).forEach(pending => await pending);
fs.writeFile("./arrayContents.json", JSON.stringify(myArray), function(err) {
    if(err) {
        console.log(err);
    }
    console.log("Some Message");
return myArray;

OR, remove the async:

const myArray = [];
const htmlString = await rp(url);
$('a','#atozindex', htmlString).map((index, element) => {
    let link = $(element).attr('href');
    if (link) {
        //Do something
        myArray.push({ item1, item2, item3 });
    }
});
fs.writeFile("./arrayContents.json", JSON.stringify(myArray), function(err) {
    if(err) {
        console.log(err);
    }
    console.log("Some Message");
return myArray;