Path: csiph.com!usenet.pasdenom.info!gegeweb.org!eternal-september.org!feeder.eternal-september.org!news.swapon.de!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail
From: "Mel Smith" <syntel@cox.net>
Newsgroups: comp.lang.javascript
Subject: Re: Puzzling JS Error
Date: Thu, 9 Apr 2015 16:26:11 -0600
Lines: 123
Message-ID: <coock9Fadg0U1@mid.individual.net>
References: <consduF625qU1@mid.individual.net> <XnsA477E3791CCF3eejj99@194.109.133.246>
X-Trace: individual.net CY4VaAAPgmgifxBykJPDWQmJNm5+I9xExr0QSAKzMs40IEJAjP
Cancel-Lock: sha1:mG95eYY6NdkTVH+i/pXRzQ3HT7w=
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 6.00.2900.5931
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157
X-RFC2646: Format=Flowed; Original
Xref: csiph.com comp.lang.javascript:27285

Hi Evertjan:

    Here is the complete Ajax set up from an *older working* Ajax 
initializer that still works. Why does this *still* work when my newer one 
fails ?

Thanks for a bit more insight into that 'throw' statement (and there is no 
visible message when the newer one 'fails'

(I'm really mixed up now)

-Mel Smith


 :


****** start of 'Older' Working Ajax initializer ********

// Make sure we haven't already been loaded
var HTTP;
if (HTTP && (typeof HTTP != "object" || HTTP.NAME)) {
    throw new Error("Namespace 'HTTP' already exists");
   }

// Create our namespace, and specify some meta-information
HTTP = {};
HTTP.NAME = "HTTP";    // The name of this namespace
HTTP.VERSION = 1.0;    // The version of this namespace

// This is a list of XMLHttpRequest creation factory functions to try
HTTP._factories = [
    function() { return new XMLHttpRequest(); },
    function() { return new ActiveXObject("Msxml2.XMLHTTP"); },
    function() { return new ActiveXObject("Microsoft.XMLHTTP"); }
];

// When we find a factory that works, store it here
HTTP._factory = null;

/**
 * Create and return a new XMLHttpRequest object.
 *
 * The first time we're called, try the list of factory functions until
 * we find one that returns a nonnull value and does not throw an
 * exception.  Once we find a working factory, remember it for later use.
 */
HTTP.newRequest = function() {
    if (HTTP._factory != null) return HTTP._factory();

    for(var i = 0; i < HTTP._factories.length; i++) {
        try {
            var factory = HTTP._factories[i];
            var request = factory();
            if (request != null) {
                HTTP._factory = factory;
                return request;
            }
        }
        catch(e) {
            continue;
        }
    }

    // If we get here, none of the factory candidates succeeded,
    // so throw an exception now and for all future calls.
    HTTP._factory = function() {
        throw new Error("XMLHttpRequest not supported");
    }
    HTTP._factory(); // Throw an error
}

HTTP.post = function(url, values, callback) {
    var request = HTTP.newRequest();
    request.open("POST", url);
    // This header tells the server how to interpret the body of the request
    request.setRequestHeader("Content-Type",
                             "application/x-www-form-urlencoded");


    request.onreadystatechange = function() {
        if (request.readyState == 4) {
            if (request.status == 200 ) {
                callback(request.responseText);
            }
            else {
                callback(request.status);
            }
        }
    }


    // Encode the properties of the values object and send them as
    // the body of the request.
    request.send(HTTP.encodeFormData(values));
    scrrequest=request; // set global vrbl screquest
};

/**
 * Encode the property name/value pairs of an object as if they were from
 * an HTML form, using application/x-www-form-urlencoded format
 */
HTTP.encodeFormData = function(data) {
    var pairs = [];
    var regexp = /%20/g; // A regular expression to match an encoded space

    for(var name in data) {
        var value = data[name].toString();
        // Create a name/value pair, but encode name and value first
        // The global function encodeURIComponent does almost what we want,
        // but it encodes spaces as %20 instead of as "+". We have to
        // fix that with String.replace()
        var pair = encodeURIComponent(name).replace(regexp,"+") + '=' +
            encodeURIComponent(value).replace(regexp,"+");
        pairs.push(pair);
    }

    // Concatenate all the name/value pairs, separating them with &
    return pairs.join('&');
};
***** end of older *working* Ajax setup ****