Constructor XHR

XHR constructor function.

• Syntax XHR new XHR([ Number timeout , [ Number retries ]])
  
  Creates and returns a new XHR object.
• Parameters

  Number timeout (Optional)

  The timeout for requests in milleseconds

  Number retries (Optional)

  Number of retries on timeout before aborting request.

• Return value A new XHR object
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  Source

  Unless otherwise noted all code in the JSLab Standard Library is licensed as GPLv3. See http://www.gnu.org/licenses/gpl.html for the entire license.

  // ************************************************************************** // Copyright 2007 - 2009 Tavs Dokkedahl // Contact: http://www.jslab.dk/contact.php // // This file is part of the JSLab Standard Library (JSL) Program. // // JSL is free software; you can redistribute it and/or modify // it under the terms of the GNU General Public License as published by // the Free Software Foundation; either version 3 of the License, or // any later version. // // JSL is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // // You should have received a copy of the GNU General Public License // along with this program. If not, see <http://www.gnu.org/licenses/>. // *************************************************************************** // http://www.w3.org/TR/XMLHttpRequest/ // Constructor function XHR(timeout, retries) { if (!XHR.factory) throw new Error('XHR: XMLHttpRequest not supported'); // Actual XMLHttpRequest object this.req = XHR.factory(); // Pseudo readyState property. Used to work around second state of 1 in IE and Firefox this._readyState = XHR.READYSTATE_UNINITIALIZED; // Work around for IE and Firefox this.aborted = false; // Set onreadystatechange var that = this; this.req.onreadystatechange = function(){that._onreadystatechange();}; // Timeout for reuest in milliseconds. Default value is 30 seconds this.timeout = timeout ? timeout : 30000; // Ref. to opaque value returned by window.setTimeout for clearing setTimeout this.timeoutRef = null; // Parameters from open and send call for recreating request when retrying. this.retryParams = {}; // Number of retires. 0 is default this.retries = retries ? retries : 0; } // Request id. Set and incremented when request is sent XHR.ridCounter = 0; // readyState constants XHR.READYSTATE_UNINITIALIZED = 0; XHR.READYSTATE_OPEN = 1; XHR.READYSTATE_SENT = 2; XHR.READYSTATE_RECIEVING = 3; XHR.READYSTATE_LOADED = 4; // Define factory function // Execute as anomymous function. Only executed once (function() { try { // Provoke error if XMLHttpRequest does not exist new XMLHttpRequest(); XHR.factory = function() { return new XMLHttpRequest(); }; } catch(e) { try { // Provoke error if ActiveXObject("Msxml2.XMLHTTP") does not exist new ActiveXObject("Msxml2.XMLHTTP"); XHR.factory = function() { return new ActiveXObject("Msxml2.XMLHTTP"); }; } catch(e) { try { // Provoke error if ActiveXObject("Microsoft.XMLHTTP") does not exist new ActiveXObject("Microsoft.XMLHTTP"); XHR.factory = function() { return new ActiveXObject("Microsoft.XMLHTTP"); }; } catch(e) { XHR.factory = null; } } } })(); // Generic onreadystatechange for all request XHR.prototype._onreadystatechange = function() { // Work around for duplicate state 1 for IE and Firefox if (this._readyState == XHR.READYSTATE_OPEN && this.req.readyState == XHR.READYSTATE_OPEN) return; this._readyState = this.req.readyState; // Work around for request.abort triggering change to readystate 4 // in IE and Firefox if (this.req.readyState == XHR.READYSTATE_LOADED && this.aborted) return; // Switch on request object readystate switch (this.req.readyState) { // open() not called yet case XHR.READYSTATE_UNINITIALIZED: this.aborted = false; break; // open() called, send() not called yet case XHR.READYSTATE_OPEN: // Set request ID this.rid = XHR.ridCounter++; // User defined event handler for state if (this.onreadystateopen) this.onreadystateopen(); break; // send() called, no respons yet case XHR.READYSTATE_SENT: // Code placed here is *not* executed until repsonse is recieved. // This is a bug in IE, Firefox and Safari. It works correctly in Opera 9 // User defined event handler is moved to XHR.prototype.send function break; // Recieving respons case XHR.READYSTATE_RECIEVING: // User defined event handler for state if (this.onreadystaterecieving) this.onreadystaterecieving(); break; // Response complete case XHR.READYSTATE_LOADED: // Clear timeout if exist if (this.timeoutRef) { window.clearTimeout(this.timeoutRef); this.timeoutRef = null; } // Get transmission time this.time = (new Date()).getTime() - this.time; // User defined event handler for state if (this.onreadystateloaded) this.onreadystateloaded(); // Response has been handled. Any cleanup code goes here // Break possible circular ref. between XHR and XMLHttpRequest objects this.breakRef(); break default: break; } }; // Break cicular reference between XHR and XMLHttpRequest object XHR.prototype.breakRef = function() { this.req.onreadystatechange = null; this.req = null; }; // Generic event function for timeout XHR.prototype._ontimeout = function() { // First action should be to abort. Thus ontimeout is *always* fired after onabort this.abort(); // Clear window.setTimeout opaque value this.timeoutRef = null; // User event handler for timeout if provided if (this.ontimeout) this.ontimeout(); // Retry if there are any retries left if (this.retries > 0) this.retry(); }; // Generic event function for retry XHR.prototype._onretry = function() { this.retries--; // User event handler for retrying if provided if (this.onretry) this.onretry(); // Reset XHR obeject (don't know why we have to make a new XMLHttpRequest object) this.reset(); // Re-open command this.open(this.retryParams.method, this.retryParams.url, this.retryParams.async, this.retryParams.username, this.retryParams.password); // Re-send command this.send(this.retryParams.body); }; // Generic event function for abort XHR.prototype._onabort = function() { this.aborted = true; // Cancel request. This will trigger a change in readystate to 4 in IE and Firefox // Safari does not reset readystate to 0 this.req.abort(); // User event handler for abortion if provided if (this.onabort) this.onabort(); };