AJAX Discussion part 1

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Javascipt Cheatsheet AJAX Cheatsheet Khởi tạo đối tượng XMLHttpRequest (XHR) PHP Code: [b]function [/b][b]createXHRobj()[/b] { if (window.XMLHttpRequest) req = new XMLHttpRequest() // browsers besides IE else if (window.ActiveXObject) req = new ActiveXObject("Microsoft.XMLHTTP") // IE else alert ("Could not create XHR obj!") return req }

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Javascipt Cheatsheet
AJAX Cheatsheet Khởi tạo đối tượng XMLHttpRequest (XHR) PHP Code: [b]function [/b][b]createXHRobj()[/b] { if (window.XMLHttpRequest) req = new XMLHttpRequest() // browsers besides IE else if (window.ActiveXObject) req = new ActiveXObject("Microsoft.XMLHTTP") // IE else alert ("Could not create XHR obj!") return req } Asynchronous GET request PHP Code: var req=createXHRobj() function request(url) { req.onreadystatechange = callbackFunction req.open("GET", url, true) // 3rd param specifies asynchronous request (browser does not wait/block) req.send("") } function callbackFunction() { if (req.readyState == 4) // request completed if (req.status == 200) // HTTP response code (200 == OK) response = req.responseText // and anything else you might need to do else { // error reporting code } }
Synchronous GET request PHP Code: function request(url) { req=createXHRobj() req.open("GET", url, false) req.send(null) alert(req.responseText) } Sending via POST - req.send() PHP Code: function submitform(url) { req=createXHRobj() // DO NOT EVER use the same names for javascript variables and // HTML element ids, they share the same namespace under IE and // may also cause problems in other browsers. namevar=encodeURIComponent(document.getElementById('Sender_Name').value) emailvar=encodeURIComponent(document.getElementById('Sender_Email').value) req.open("POST", url, false) // req.setRequestHeader() must come AFTER req.open() req.setRequestHeader("Content-Type","application/x-www-form-urlencoded") req.send("name="+namevar+"&email="+emailvar) alert(req.responseText) } // we do away with HTML form submit to simplify things // long descriptive names that will not be use d as // javascript variable names are a good habit here...
Wrapper code for Asynchronous requests PHP Code: var req1=createXHRobj() var req2=createXHRobj() function asynXHR(url, reqobj, action) { reqobj.onreadystatechange=action reqobj.open("GET", url, true) reqobj.send("") } function responseIsReady(reqobj) { if (reqobj.readyState==4) if (reqobj.status==200) return true else { alert("ERROR: STATUS RESPONSE "+reqobj.status) return true // let the call proceed so we know which // call the status error occurred in } else return false } // each callback function must use its own request object var req1, req2 function showstock() { if (responseIsReady(req1)) alert("stock price: $"+req1.responseText) /* IE can't reuse the XHR object, you are required to clean up and create a new one */ req1=null req1=createXHRobj() } function showtemp() { if (responseIsReady(req2)) alert("It's "+req2.responseText+" celsius") /* IE can't reuse the XHR object, you are required to clean up and create a new one */ req2=null req2=createXHRobj()
} asynXHR("price.php?stock=GOOG",req1,showstock) asynXHR("temperature.php?city=Singapore",req2,showtemp) One.N(UDS)