Accessing array inside object in node js - undefined?

Question

In javascript:

var post = {};
post.arr = ["hi", "hello"];
$.post("http://localhost:8000/test", post);

and in node:

        var body = "";
    request.on('data', function (data) {
        body += data
    });
    request.on('end', function (data) {
        var post = qs.parse(body);
        console.log(post); // I see { 'arr[]': ['hi', 'hello'] };
        console.log(post.arr); // undefined
    }

Any idea what might have caused this?

If that's exactly what you see then you just have a string which isn't a valid object (can't have single quotes or semicolons in JSON). If it is an object and you're printing it incorrectly, then you have an object with a key arr[] so you can access it as post['arr[]']. — Mike Cluck
– Mike Cluck, Commented Apr 15, 2016 at 16:30
Because when jQuery POSTs an array, it adds [] to indicate it's an array. Many languages and frameworks take advantage of this to automatically parse arrays. — Mike Cluck
– Mike Cluck, Commented Apr 15, 2016 at 16:37

Community · Accepted Answer · 2017-05-23 10:28:14Z

1

Based on your comments, it looks like somehow the map key is literally arr[]. Try console.log(post['arr[]']);

jQuery will modify the name of arrays as @MikeC pointed out. More info here: https://stackoverflow.com/a/5888057/1861459

edited May 23, 2017 at 10:28

CommunityBot

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answered Apr 15, 2016 at 16:29

pherris

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4 Comments

pherris Over a year ago

I'm guessing qs is the queryString library? See updated answer.

codingIsFun Over a year ago

data.arr gives undefined

pherris Over a year ago

yep, MikeC is right - it's jQuery changing the name. More info here: stackoverflow.com/a/5888057/1861459

codingIsFun Over a year ago

Thanks for the link.

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