如何给script标签增加可执行的javascript代码

<script>
    var rnotwhite = /\S/;
    var scriptEval = false;
    var root = document.documentElement,
		script = document.createElement("script"),
		div = document.createElement("div"),
		id = "script" + new Date().getTime();
    script.type = "text/javascript";
    try {
        script.appendChild(document.createTextNode("window." + id + "=1;"));
    } catch (e) { }
    root.insertBefore(script, root.firstChild);
    // Make sure that the execution of code works by injecting a script
    // tag with appendChild/createTextNode
    // (IE doesn't support this, fails, and uses .text instead)
    if (window[id]) {
        scriptEval = true;
        delete window[id];
    }
    // Evalulates a script in a global context
    function globalEval(data) {
        if (data && rnotwhite.test(data)) {
            // Inspired by code by Andrea Giammarchi
            // http://webreflection.blogspot.com/2007/08/global-scope-evaluation-and-dom.html
            var head = document.getElementsByTagName("head")[0] || document.documentElement,
				script = document.createElement("script");
            script.type = "text/javascript";
            if (scriptEval) {
                script.appendChild(document.createTextNode(data));
            } else {
                script.text = data;
            }
            // Use insertBefore instead of appendChild to circumvent an IE6 bug.
            // This arises when a base node is used (#2709).
            head.insertBefore(script, head.firstChild);
            head.removeChild(script);
        }
    }
    globalEval("alert('编程设计网')")
</script>