XMLHttpRequest在for循环中

尝试下面的代码段

// Javascriptwindow.onload = function(){    var f = (function(){        var xhr = [], i;        for(i = 0; i < 3; i++){ //for loop (function(i){     xhr[i] = new XMLHttpRequest();     url = "closure.php?data=" + i;     xhr[i].open("GET", url, true);     xhr[i].onreadystatechange = function(){         if (xhr[i].readyState === 4 && xhr[i].status === 200){  console.log('Response from request ' + i + ' [ ' + xhr[i].responseText + ']');          }     };     xhr[i].send(); })(i);        }    })();};// PHP [closure.php]echo "Hello Kitty -> " . $_GET["data"];

响应

Response from request 0 [ Hello Kitty -> 0]Response from request 1 [ Hello Kitty -> 1]Response from request 2 [ Hello Kitty -> 2]