HTTP Request

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Published in: JavaScript 

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Generic global code for managing XMLHttpRequest objects.

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1. // ----------------------------------------
2. // Wrapper function for constructing a request object.
3. // Parameters:
4. // reqType: The HTTP request type, such as GET or POST.
5. // url: The URL of the server program.
6. // asynch: Whether to send the request asynchronously or not.
7. // ----------------------------------------
8.  
9. function httpRequest(reqType,url,asynch) {
10.  
11. // Mozilla-based browsers
12. if (window.XMLHttpRequest) {
13. request = new XMLHttpRequest();
14. } else if (window.ActiveXObject) {
15. request = new ActiveXObject("Msxml2.XMLHTTP");
16. if (!request) {
17. request = new ActiveXObject("Microsoft.XMLHTTP");
18. }
19. }
20.  
21. // Request could still be null if neither ActiveXObject
22. // initialization succeeded
23. if (request) {
24. // If the reqType param is POST, then the fifth arg is the POSTed data
25. if (reqType.toLowerCase() != "post") {
26. initReq(reqType, url, asynch, respHandle);
27. } else {
28. // The POSTed data
29. var args = arguments[4];
30. if (args != null && args.length > 0) {
31. initReq(reqType, url, asynch, respHandle, args);
32. }
33. }
34. } else {
35. alert("Your browser does not permit the use of all " +
36. "of this application's features!");
37. }
38.  
39. }
40.  
41. // ----------------------------------------
42. // Initialize a request object that is already constructed
43. // ----------------------------------------
44.  
45. function initReq(reqType, url, bool, respHandle) {
46. try {
47. // Specify the function that will handle the HTTP response
48. request.onreadystatechange = handleResponse;
49. request.open(reqType, url, bool);
50. // If the reqType param is POST, then the
51. // fifth argument to the function is the POSTed data
52. if (reqType.toLowerCase() == "post") {
53. // Set the Content-Type header for a POST request
54. request.setRequestHeader("Content-Type", "application/x-ww-form-urlencoded; charset=UTF-8");
55. request.send(arguments[4]);
56. } else {
57. request.send(null);
58. }
59. } catch (errv) {
60. alert("The application cannot contact the server at the moment. " +
61. "Please try again in a few seconds.\n" +
62. "Error detail: " errv.message);
63. }
64. }