javascript - What does XMLHttpRequest do in that code -

i'm beginner in javascript , , want understand method xmlhttprequest does.

this code reading, , wondering if explain doing:

var xhttp; xhttp=window.xmlhttprequest?new xmlhttprequest:new activexobject("microsoft.xmlhttp"),xhttp.open("get","script.php",!0),xhttp.send(); 

hi not in explanations, try explain in details see , understand this.

the xmlhttprequest object. used exchanging of data server. use can send data script on server(request) , data it(response). response data can displayed instantly on page without page reloading. process call ajax.

i read provided code as

//define variable  var xhttp; /*assign xmlhttprequest object variable check if global object window has xmlhttprequest object if not , user have newer browser, create 1 (new xmlhttprequest -           ie7+, firefox, chrome, opera, safari browsers) or user have older browser (activexobject("microsoft.xmlhttp") - ie6, ie5 browsers) xhttp.open method specifies type of request(method get, script on server,    asynchronous) xhttp.send method sends request server*/  xhttp=window.xmlhttprequest?new xmlhttprequest:new     activexobject("microsoft.xmlhttp"),xhttp.open("get","script.php",!0),xhttp.send(); 

but have check readystate property of xmlhttprequest object well

xmlhttp.onreadystatechange = function() {     //4: request finished , response ready     //200: "ok"     if (xmlhttp.readystate == 4 && xmlhttp.status == 200) {          //display of returned data server         //it available in property - xmlhttp.responsetext     } } 

the whole peace of code should like:

if (window.xmlhttprequest) {     xmlhttp = new xmlhttprequest();                     // code ie7+, firefox, chrome, opera, safari } else {     xmlhttp = new activexobject("microsoft.xmlhttp");   // code ie6, ie5 } xmlhttp.onreadystatechange = function() {     if (xmlhttp.readystate == 4 && xmlhttp.status == 200) {          //display of returned data server         //jquery example         $('div').html(xmlhttp.responsetext);     } } xmlhttp.open("get", "script.php", true); xmlhttp.send(); 

hopefully helped, luck!