js跨域得到问题？

Question

所谓js跨域问题，是指在一个域下的页面中通过js访问另一个不同域下 的数据对象，出于安全性考 虑，几乎所有浏览器都不允许这种跨域访问，这就导致在一些ajax应用中，使用跨域的web service会成为一个问题。
可是为什么jQuery getScript 可以跨域呢？是什么原理啊？

Answer 1

if ( s.dataType === "script" && type === "GET" && remote ) {
var head = document.getElementsByTagName("head")[0] || document.documentElement;
[color=red] var script = document.createElement("script");
[/color] script.src = s.url;
if ( s.scriptCharset ) {
script.charset = s.scriptCharset;
}

        // Handle Script loading
        if ( !jsonp ) {
            var done = false;

            // Attach handlers for all browsers
            script.onload = script.onreadystatechange = function() {
                if ( !done && (!this.readyState ||
                        this.readyState === "loaded" || this.readyState === "complete") ) {
                    done = true;
                    success();
                    complete();

                    // Handle memory leak in IE
                    script.onload = script.onreadystatechange = null;
                    if ( head && script.parentNode ) {
                        head.removeChild( script );
                    }
                }
            };
        }

        // Use insertBefore instead of appendChild  to circumvent an IE6 bug.
        // This arises when a base node is used (#2709 and #4378).
        head.insertBefore( script, head.firstChild );

        // We handle everything using the script element injection
        return undefined;
    }

即动态创建script标签
[url]http://www.cnblogs.com/rainman/archive/2011/02/20/1959325.html[/url]
[url]http://505253293.blog.163.com/blog/static/26899167201282655244720/[/url]