/** * http.js: utilities for scripted HTTP requests * * From the book JavaScript: The Definitive Guide, 5th Edition, * by David Flanagan. Copyright 2006 O'Reilly Media, Inc. (ISBN: 0596101996) */ // 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 } /** * Use XMLHttpRequest to fetch the contents of the specified URL using * an HTTP GET request. When the response arrives, pass it (as plain * text) to the specified callback function. * * This function does not block and has no return value. */ HTTP.getText = function(url, callback) { var request = HTTP.newRequest(); request.onreadystatechange = function() { if (request.readyState == 4 && request.status == 200) callback(request.responseText); } request.open("GET", url); request.send(null); }; /** * Use XMLHttpRequest to fetch the contents of the specified URL using * an HTTP GET request. When the response arrives, pass it (as a parsed * XML Document object) to the specified callback function. * * This function does not block and has no return value. */ HTTP.getXML = function(url, callback) { var request = HTTP.newRequest(); request.onreadystatechange = function() { if (request.readyState == 4 && request.status == 200) callback(request.responseXML); } request.open("GET", url); request.send(null); }; /** * Use an HTTP HEAD request to obtain the headers for the specified URL. * When the headers arrive, parse them with HTTP.parseHeaders() and pass the * resulting object to the specified callback function. If the server returns * an error code, invoke the specified errorHandler function instead. If no * error handler is specified, pass null to the callback function. */ HTTP.getHeaders = function(url, callback, errorHandler) { var request = HTTP.newRequest(); request.onreadystatechange = function() { if (request.readyState == 4) { if (request.status == 200) { callback(HTTP.parseHeaders(request)); } else { if (errorHandler) errorHandler(request.status, request.statusText); else callback(null); } } } request.open("HEAD", url); request.send(null); }; /** * Parse the response headers from an XMLHttpRequest object and return * the header names and values as property names and values of a new object. */ HTTP.parseHeaders = function(request) { var headerText = request.getAllResponseHeaders(); // Text from the server var headers = {}; // This will be our return value var ls = /^\s*/; // Leading space regular expression var ts = /\s*$/; // Trailing space regular expression // Break the headers into lines var lines = headerText.split("\n"); // Loop through the lines for(var i = 0; i < lines.length; i++) { var line = lines[i]; if (line.length == 0) continue; // Skip empty lines // Split each line at first colon, and trim whitespace away var pos = line.indexOf(':'); var name = line.substring(0, pos).replace(ls, "").replace(ts, ""); var value = line.substring(pos+1).replace(ls, "").replace(ts, ""); // Store the header name/value pair in a JavaScript object headers[name] = value; } return headers; }; /** * Send an HTTP POST request to the specified URL, using the names and values * of the properties of the values object as the body of the request. * Parse the server's response according to its content type and pass * the resulting value to the callback function. If an HTTP error occurs, * call the specified errorHandler function, or pass null to the callback * if no error handler is specified. **/ HTTP.post = function(url, values, callback, errorHandler) { var request = HTTP.newRequest(); request.onreadystatechange = function() { if (request.readyState == 4) { if (request.status == 200) { callback(HTTP._getResponse(request)); } else { if (errorHandler) errorHandler(request.status, request.statusText); else callback(null); } } } 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"); // Encode the properties of the values object and send them as // the body of the request. request.send(HTTP.encodeFormData(values)); }; /** * 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('&'); }; /** * Parse an HTTP response based on its Content-Type header * and return the parsed object */ HTTP._getResponse = function(request) { // Check the content type returned by the server switch(request.getResponseHeader("Content-Type")) { case "text/xml": // If it is an XML document, use the parsed Document object return request.responseXML; case "text/json": case "application/json": case "text/javascript": case "application/javascript": case "application/x-javascript": // If the response is JavaScript code, or a JSON-encoded value, // call eval() on the text to "parse" it to a JavaScript value. // Note: only do this if the JavaScript code is from a trusted server! return eval(request.responseText); default: // Otherwise, treat the response as plain text and return as a string return request.responseText; } }; /** * Send an HTTP GET request for the specified URL. If a successful * response is received, it is converted to an object based on the * Content-Type header and passed to the specified callback function. * Additional arguments may be specified as properties of the options object. * * If an error response is received (e.g., a 404 Not Found error), * the status code and message are passed to the options.errorHandler * function. If no error handler is specified, the callback * function is called instead with a null argument. * * If the options.parameters object is specified, its properties are * taken as the names and values of request parameters. They are * converted to a URL-encoded string with HTTP.encodeFormData() and * are appended to the URL following a '?'. * * If an options.progressHandler function is specified, it is * called each time the readyState property is set to some value less * than 4. Each call to the progress handler function is passed an * integer that specifies how many times it has been called. * * If an options.timeout value is specified, the XMLHttpRequest * is aborted if it has not completed before the specified number * of milliseconds have elapsed. If the timeout elapses and an * options.timeoutHandler is specified, that function is called with * the requested URL as its argument. **/ HTTP.get = function(url, callback, options) { var request = HTTP.newRequest(); var n = 0; var timer; if (options.timeout) timer = setTimeout(function() { request.abort(); if (options.timeoutHandler) options.timeoutHandler(url); }, options.timeout); request.onreadystatechange = function() { if (request.readyState == 4) { if (timer) clearTimeout(timer); if (request.status == 200) { callback(HTTP._getResponse(request)); } else { if (options.errorHandler) options.errorHandler(request.status, request.statusText); else callback(null); } } else if (options.progressHandler) { options.progressHandler(++n); } } var target = url; if (options.parameters) target += "?" + HTTP.encodeFormData(options.parameters) request.open("GET", target); request.send(null); }; HTTP.getTextWithScript = function(url, callback) { // Create a new script element and add it to the document var script = document.createElement("script"); document.body.appendChild(script); // Get a unique function name var funcname = "func" + HTTP.getTextWithScript.counter++; // Define a function with that name, using this function as a // convenient namespace. The script generated on the server // invokes this function HTTP.getTextWithScript[funcname] = function(text) { // Pass the text to the callback function callback(text); // Clean up the script tag and the generated function document.body.removeChild(script); delete HTTP.getTextWithScript[funcname]; } // Encode the URL we want to fetch and the name of the function // as arguments to the jsquoter.php server-side script. Set the src // property of the script tag to fetch the URL script.src = "jsquoter.php" + "?url=" + encodeURIComponent(url) + "&func=" + encodeURIComponent("HTTP.getTextWithScript." + funcname); } // We use this to generate unique function callback names in case there // is more than one request pending at a time. HTTP.getTextWithScript.counter = 0;
