Looping Through JSON

Question

I have a JSON object:

 var json = {"Mike":1, "Jake":1, "Henry":1};

I am trying to loop through this list to access the names. Currently I am using:

for (var name in json) {
    if (json.hasOwnProperty(name)) {
        console.log(name);
    }
}

But it's not printing the name. Is that the correct way to do it?

jsFiddle: http://jsfiddle.net/bKwYq/

Working for me, code looks fine. You realize console.log() prints to a debugger console and not to your page, yes? — Interrobang, Dec 07 '11 at 19:49
@Interrobang Yes. In the console though I am seeing the number 1. Very strange. — James Guvna Jeffery, Dec 07 '11 at 19:52
Note that there is no JSON here whatsoever. JSON is a _text-based_ data format that is based on, is named after and _looks like_ this fundamental syntax of Javascript that you're using, which could be called Object Notation. — Lightness Races in Orbit, Dec 07 '11 at 20:03
Side note: that is not a [JSON object](http://json.org); that is a JavaScript object literal. A JSON object would look like: `var json = '{"Mike":1, "Jake":1, "Henry":1}';` — Phrogz, Dec 07 '11 at 20:04
He is asking how to print the names, he's not telling you that this example does not output to the console. — Dominic Goulet, Dec 07 '11 at 20:08

score 0 · Answer 1 · answered Oct 15 '22 at 10:40

It can be done by getting the key using Object.keys and then using foreach loop to print to console or display as alert message.

var persons = {"Mike":1, "Jake":1, "Henry":1};
var keysInPerson= Object.keys (persons);
keysInPerson.forEach ((name) => console.log (name));

//Alert
keysInPerson.forEach ((name) => alert (name));

score 0 · Answer 2 · answered Dec 07 '11 at 20:09

0

As other people mentioned, this is not JSON, it's just an object.

The hasOwnProperty thing may not really be necessary here also.

var persons = {"Mike":1, "Jake":1, "Henry":1};
for (var name in persons) {
    alert(name);
}

This will work in every browser: http://jsfiddle.net/HsNMY/

answered Dec 07 '11 at 20:09

Jamund Ferguson

16,721
3
42
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It will not work as intended if you add `Object.prototype.foo = 42` before your loop. This is why `hasOwnProperty` is recommended. – Phrogz Dec 07 '11 at 21:00
it's super recommended to not add anything to Object.prototype.foo, so all major libraries don't. – Jamund Ferguson Dec 07 '11 at 21:23
While I know that some major libraries forbid it (because they don't want to add `hasOwnProperty` in all their enumerations due to the speed hit), I'd like you to provide a citation for "super recommended". – Phrogz Dec 07 '11 at 21:26
http://stackoverflow.com/questions/6877005/extending-object-prototype-javascript http://javascriptweblog.wordpress.com/2011/12/05/extending-javascript-natives/ http://erik.eae.net/archives/2005/06/06/22.13.54/ Extending natives I think is cool though, just not Object.prototype. This is great talk about it: http://blip.tv/jsconf/jsconf2011-andrew-dupont-everything-is-permitted-extending-built-ins-5211542 – Jamund Ferguson Dec 07 '11 at 21:33
Thanks. FWIW I personally find only the second URL convincing; the first is just a random opinion, and the third appears to be written by someone who clearly didn't understand how to write JavaScript code. Still, you have provided a citation as asked. :) – Phrogz Dec 07 '11 at 21:36
:) that video i posted about extending natives goes pretty deep into it though. – Jamund Ferguson Dec 07 '11 at 21:38

score -2 · Answer 3 · answered Dec 07 '11 at 20:08

-2

The correct way to PRINT the name is to use document.write instead of console.log, as in this fiddle :

http://jsfiddle.net/jRAna/

answered Dec 07 '11 at 20:08

Dominic Goulet

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7
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console.log is actually a nicer way to debug rather than printing to the page – TS- Dec 07 '11 at 21:21
wow so much hatred simply by responding to the actual question. Never said it was better to print it, just answered what was asked. – Dominic Goulet Dec 07 '11 at 23:59

Looping Through JSON

3 Answers3