这段js的作用是什么？异步加载么？

var Base = {
    head: document.getElementsByTagName("head")[0] || document.documentElement,
    Myload: function(B, A) {
        this.done = false;
        B.onload = B.onreadystatechange = function() {
            if (!this.done && (!this.readyState || this.readyState === "loaded" || this.readyState === "complete")) {
                this.done = true;
                A();
                B.onload = B.onreadystatechange = null;
                if (this.head && B.parentNode) {
                    this.head.removeChild(B)
                }
            }
        }
    },
    getScript: function(A, C) {
        var B = function() {};
        if (C != undefined) {
            B = C
        }
        var D = document.createElement("script");
        D.setAttribute("language", "javascript");
        D.setAttribute("type", "text/javascript");
        D.setAttribute("src", A);
        this.head.appendChild(D);
        this.Myload(D, B)
    },
    getStyle: function(A, CB) {
        var B = function() {};
        if (CB != undefined) {
            B = CB
        }
        var C = document.createElement("link");
        C.setAttribute("type", "text/css");
        C.setAttribute("rel", "stylesheet");
        C.setAttribute("href", A);
        this.head.appendChild(C);
        this.Myload(C, B)
    }
}

定义了一个可以动态生成script标签和link标签的对象

GetVerNum() 功能类似于生成随机数时间戳

Base.getScript('/statics/js/B.js?v=' + GetVerNum())调用了Base.getScript()，并传入了参数A

getScript()运行时在head中的script中加载了地址为/statics/js/B.js的js文件后调用了Myload()

B.onload = B.onreadystatechange = function() {
            if (!this.done && (!this.readyState || this.readyState === "loaded" || this.readyState === "complete")) {
                this.done = true;
                A();
                B.onload = B.onreadystatechange = null;
                if (this.head && B.parentNode) {
                    this.head.removeChild(B)
                }
            }
        }

此时B为document.createElement("script")，该方法的调用绑定了当页面状态改变时移除head中的script标签的事件

在script标签中appendChild应该还是一个阻塞的过程吧，只是这个加载过程发生在页面onload之后