对node.js服务器的AJAX调用返回未定义

Question

I am trying to access a string that is returned by a serverside Node.js function.

function createString () {
    do something ...
    console.log(finalString);
    return finalString;
};

I am using a plain JavaScript AJAX request to GET the string from the server

const xhr = new XMLHttpRequest();
xhr.onreadystatechange = function () {
    do something ...
};
xhr.open('GET', 'http://localhost:5000/array');
xhr.send();

My serverside looks like:

app.get('/array', (req, res) => {
        console.log('request received');
        console.log(createString());
        res.send(createString());
    }
);

createString() is always returning as 'undefined' for the AJAX request even though it is logging the correct string in finalString.

I believe the issue is the asynchronous aspect of AJAX but I am not sure how to tell res.send() to wait until createString() runs .

Any help is appreciated!

Answer 1

You can pass the req and res objects to your createString function. (I am assuming that your createArray is a typo, and should be createString ). Indeed if you have just this function, you can simply have:

server.js

app.get('/array', createString);

createString.js

function createString (req, res) {
    do something ...
    console.log(finalString);
    return res.status(200).send(finalString);
};