JavaScript get_headers

fetches all the headers sent by the server in response to a HTTP request

function get_headers (url, format) {
    // +   original by: Paulo Freitas
    // +    bugfixed by: Brett Zamir (http://brett-zamir.me)
    // %        note 1: This function uses XmlHttpRequest and cannot retrieve resource from different domain.
    // %        note 1: Synchronous so may lock up browser, mainly here for study purposes.    // *     example 1: get_headers('http://kevin.vanzonneveld.net/pj_test_supportfile_1.htm')[0];
    // *     returns 1: 'Date: Wed, 13 May 2009 23:53:11 GMT'
    var req = this.window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : new XMLHttpRequest();
    if (!req) {
        throw new Error('XMLHttpRequest not supported');    }
    var tmp, headers, pair, i, j = 0;
 
    req.open('HEAD', url, false);
    req.send(null); 
    if (req.readyState < 3) {
        return false;
    }
     tmp = req.getAllResponseHeaders();
    tmp = tmp.split('\n');
    tmp = this.array_filter(tmp, function (value) { return value.substring(1) !== ''; });
    headers = format ? {} : [];
     for (i in tmp) {
        if (format) {
            pair = tmp[i].split(':');
            headers[pair.splice(0, 1)] = pair.join(':').substring(1);
        } else {            headers[j++] = tmp[i];
        }
    }
    return headers;
}

external links: original PHP docs | raw js source

Examples

Running

1	get_headers('http://kevin.vanzonneveld.net/pj_test_supportfile_1.htm')[0];

Should return

1	'Date: Wed, 13 May 2009 23:53:11 GMT'

Dependencies

No dependencies, you can use this function standalone.

Open syntax issues

php.js uses JsLint to help us keep our code consistent and prevent some common bugs.

Eventually we want all code to pass or at least take into consideration most fixes suggested by JsLint, following this JsLint configuration we’ve decided on.

Authors

Thanks to the following developers, you get to have get_headers goodness in JavaScript.

Paulo Freitas ( original )
Brett Zamir ( bugfixed )

Comments

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Use:

[CODE]
your_stuff('here');
[/CODE]

for proper code formatting
By submitting code here you are allowing us to use it in php.js hence dual licensing it under the MIT and GPL licenses

Kevin van Zonneveld
10 Dec '08

@ Paulo Ricardo F. Santos: hehe, no problem! Thanks for giving the final function complete though, makes my job a little easier :)

Paulo Ricardo F. Santos
4 Dec '08

OMG! Sorry for the flood and ignore my last 2 comments (#7 and #8 - I was quite confused). Here's the function with corrections:

[code="javascript"]
function get_headers(url, format) {
var req = window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : new XMLHttpRequest();
if (!req) throw new Error('XMLHttpRequest not supported');
var tmp, headers, pair, i;

req.open('HEAD', url, false);
req.send(null);

if (req.readyState < 3) {
return false;
}

tmp = req.getAllResponseHeaders();alert(tmp);
tmp = tmp.split('\n');
tmp = array_filter(tmp, function (value) { return value.substring(1) != ''; });
headers = [req.status + ' ' + req.statusText];

for (i in tmp) {
if (format) {
pair = tmp[i].split(':');
headers[pair.splice(0, 1)] = pair.join(':').substring(1);
} else {
headers[headers.length] = tmp[i];
}
}

return headers;
}
[/code]
About the Opera problem, I don't know how to fix it. In my tests, Opera 9.62 returned a empty string in statusText property and getAllResponseHeaders() function - only status property returned as expected. Both Firefox 3 and IE 7 worked perfectly. :)

Paulo Ricardo F. Santos
4 Dec '08

Ah! This line:

headers[pair.splice(0, 1)] = pair.join(':').replace(/^\s+|\s+$/g, '');

might be only this, there's no difference:

headers[pair.splice(0, 1)] = pair.join(':');

And as far I've noted, to work properly in Opera, the AJAX request should be asynchronized, as here: http://www.ceciliadassi.com/get_headers2.js. Synchronized requests returns false in the most of times. ;/

Paulo Ricardo F. Santos
4 Dec '08

Hmm, might be useful replace

[code="javascript"]tmp.pop();[/code]

to

[code="javascript"]tmp = array_filter(tmp, function (str) { return str.replace(/^\s+|\s+$/g, '') != ''; });[/code]

to avoid any unexpected problem. ;)

Paulo Ricardo F. Santos
4 Dec '08

Oops, sorry for the inconvenient - it's a bit buggy and I don't know how it worked before.

This snippet should fixes all the problems:

[code="javascript"] tmp = req.getAllResponseHeaders().split('\n');
tmp.pop();
headers = [req.status + ' ' + req.statusText];

for (i in tmp) {
if (format) {
pair = tmp[i].split(':');
headers[pair.splice(0, 1)] = pair.join(':').replace(/^\s+|\s+$/g, '');
} else {
headers[headers.length] = tmp[i];
}
}[/code]

Here's a temporary demo - working as expected: http://www.ceciliadassi.com/get_headers.html

[]'s

Kevin van Zonneveld
3 Dec '08

@ Paulo Ricardo F. Santos: I'm testing from console using the ./phpjstest.php file in the _tools directory in svn. But what's strange is that code from file_size (which I thought was identical) does not break.

Paulo Ricardo F. Santos
3 Dec '08

@ Kevin: Ah! Well... how you are testing? AFAIK, there's no way to test it locally or request a cross-domain address. I've tested it on my test domain, requesting a file from same server. ;)

Kevin van Zonneveld
3 Dec '08

@ Paulo Ricardo F. Santos: Well I haven't got it working yet, so that's why the examples are still in a copy-pasted state.

Paulo Ricardo F. Santos
3 Dec '08

@ Kevin: Hmm, great idea, I forgot this possible abnormal behavior! >.<

Ah!, man, I don't understood your example. Why it should returns 123? o.O

Kevin van Zonneveld
3 Dec '08

@ Paulo Ricardo F. Santos: In my test suite: phpjstest.php, readyState would stay at 1, I had to build a condition < 3 to avoid the function from crashing. Very strange, because the file_exists function uses the same code and that works ok.

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