I have a url contain all the json format.
function load() { dashcode.setupParts(); var link = 'http://api.musixmatch.com/ws/1.1/track.search?apikey=d34fb59a16877bd1c540aa472491825b&q_track=back%20to%20december&page_size=10'; req.open = ("GET", link, false); req.onreadystatechange = readXML(); req.send(null); } function readXML(){ alert(req.responseText); } this code keep saying null all the time. Are there any way that i can retrieved those json text
The problem is with req.onreadystatechange = readXML();. You're assigning the result of the function instead of the function itself (as a callback).
You want req.onreadystatechange = readXML;. Though I must say I'm not sure how this code is supposed to work. Not in terms of how the XHR is made, nor with regards to the external domain.
Correct usage is as follows.You can check this link http://jsfiddle.net/UH4KY/1/ The link will alert undefined since cross domain scripting is not allowed .You can set the Access-Control-Allow-Origin and test the code. function readXML(req) { alert(req); }
function load() { var xmlhttp; if (window.XMLHttpRequest) { // code for IE7+, Firefox, Chrome, Opera, Safari xmlhttp = new XMLHttpRequest(); } else { // code for IE6, IE5 xmlhttp = new ActiveXObject("Microsoft.XMLHTTP"); } var link = 'http://api.musixmatch.com/ws/1.1/track.search?apikey=d34fb59a16877bd1c540aa472491825b&q_track=back%20to%20december&page_size=10'; //req.open = ("GET", link, false); xmlhttp.onreadystatechange = function(){ alert(xmlhttp.responseText); } xmlhttp.open("GET", link, false); xmlhttp.send(null); } 
readXMLdirectly and assign its return value toonreadystatechangeinstead of the function itself. Also note that you cannot simply make requests to 3rd party domains. You'd have to make use of JSONP, which the server has to support.