What is the equivalent of Array.prototype.map() for objects in JavaScript

Question

I am trying to take some some objects from an original object into an array variable.

console.log("news len", news["articles"].length); // this comes out to 9

for(var a in news["articles"]) {
    var results = [];
    results.push({
        title:news["articles"][a]["title"],
        subtitle: news["articles"][a]["description"],
        item_url:news["articles"][a]["title"],
        image_url:news["articles"][a]["urlToImage"],
    });
}
console.log("results len",results.length); //only contains one entry

Is there another way to accomplish this, and if not what am I doing wrong?

Using Node js if that helps any.

can you add your object news ,how does the content look in it — Geeky
– Geeky, Commented Dec 3, 2016 at 23:01
It looks like news["articles"] is an array, so we not just map with that? — Jordan Soltman
– Jordan Soltman, Commented Dec 3, 2016 at 23:02
to prevent some errors, like reinitializing empty array, i suggest to declare all variables in advance at the beginning of the code, directly after the functions - this includes variable for for, as well. — Nina Scholz
– Nina Scholz, Commented Dec 3, 2016 at 23:09

Nina Scholz · Accepted Answer · 2016-12-03 23:05:27Z

3

You could use map directly and return an object in the callback for a new array

var results = news.articles.map(function (a) {
        return {
            title: a.title,
            subtitle: a.description,
            item_url: a.title,
            image_url: a.urlToImage
        };
    };

answered Dec 3, 2016 at 23:05

Nina Scholz

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1 Comment

crod Over a year ago

Yup, I was using the news object itself instead of news.articles. Lapse of thinking on my part, thanks!

ruakh · Accepted Answer · 2016-12-03 23:02:21Z

2

The main problem is that each iteration of your loop re-sets results to an empty array:

var results=[];

If you move that statement before your loop, you will get something closer to what you want.

That said, it looks like news["articles"] already is an array, so you can probably just use Array.prototype.map?

answered Dec 3, 2016 at 23:02

ruakh

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Jordan Soltman · Accepted Answer · 2016-12-03 23:04:07Z

0

var results = [];
news["articles"].map(function(val,idx){
    results.push({
       title: val["title"],
       //etc
    }
});

answered Dec 3, 2016 at 23:04

Jordan Soltman

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