1、XMLHttpRequest对象的OPEN方法和SEND方法的作用是什么哟? 2、OPEN方法的第3个参数有什么作用呢？为TRUE或FALSE对后面SEND方法的执行有什么影响呢？

The foundation that makes AJAX possible is the communication layer with the server. The most complete option for performing this communication is the JavaScript XMLHttpRequest object. If ...