Dispatching an XMLHttpRequest

Thu Jul 30, 2009 10:02 am

Dispatching an XMLHttpRequest
I'll start at the beginning of the Ajax sequence: creating and dispatching an XMLHttpRequest from the browser. Unfortunately, the method to create an XMLHttpRequest differs from browser to browser. The JavaScript function in Listing 2 smoothes out these browser-dependent wrinkles, detecting the correct approach for the current browser and returning an XMLHttpRequest ready to use. It's best to think of this as boilerplate code: simply copy it into your JavaScript library and use it when you need an XMLHttpRequest.

Code:: /* * Returns a new XMLHttpRequest object, or false if this browser * doesn't support it */ function newXMLHttpRequest() { var xmlreq = false; if (window.XMLHttpRequest) { // Create XMLHttpRequest object in non-Microsoft browsers xmlreq = new XMLHttpRequest(); } else if (window.ActiveXObject) { // Create XMLHttpRequest via MS ActiveX try { // Try to create XMLHttpRequest in later versions // of Internet Explorer xmlreq = new ActiveXObject("Msxml2.XMLHTTP"); } catch (e1) { // Failed to create required ActiveXObject try { // Try version supported by older versions // of Internet Explorer xmlreq = new ActiveXObject("Microsoft.XMLHTTP"); } catch (e2) { // Unable to create an XMLHttpRequest with ActiveX } } } return xmlreq; }

Dispatching an XMLHttpRequest

Dispatching an XMLHttpRequest

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