XMLHTTP 跨浏览器的用法

//Create a boolean variable to check for a valid Internet Explorer instance.

var xmlhttp = false;

//Check if we are using IE.

try {

//If the Javascript version is greater than 5.

xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");

alert ("You are using Microsoft Internet Explorer.");

} catch (e) {

//If not, then use the older active x object.

try {

//If we are using Internet Explorer.

xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");

alert ("You are using Microsoft Internet Explorer");

} catch (E) {

//Else we must be using a non-IE browser.

xmlhttp = false;

}

}

//If we are using a non-IE browser, create a javascript instance of the object.

if (!xmlhttp && typeof XMLHttpRequest != 'undefined') {

xmlhttp = new XMLHttpRequest();

alert ("You are not using Microsoft Internet Explorer");

}

更简单的方法：

var xmlhttp;

//If, the activexobject is available, we must be using IE.

if (window.ActiveXObject){

xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");

} else {

//Else, we can use the native Javascript handler.

xmlhttp = new XMLHttpRequest();

}