JS代码逻辑感觉有些疑惑

JS代码如下：

KISSY.add("io/base", ["event/custom", "promise"], function(d, f) {
    function i(b) {
        var a = b.context;
        delete b.context;
        b = d.mix(d.clone(n), b, {
            deep: !0
        });
        b.context = a || b;
        var l, j = b.type, g = b.dataType, a = b.uri = m.resolve(b.url);
        b.uri.setQuery("");
        "crossDomain"in b || (b.crossDomain = !b.uri.isSameOriginAs(m));
        j = b.type = j.toUpperCase();
        b.hasContent = !e.test(j);
        if (b.processData && (l = b.data) && "string" !== typeof l)
            b.data = d.param(l, void 0, void 0, b.serializeArray);
        g = b.dataType = d.trim(g || "*").split(c);
        !("cache"in b) && d.inArray(g[0], ["script", "jsonp"]) && (b.cache = !1);
        b.hasContent || (b.data && a.query.add(d.unparam(b.data)),
        !1 === b.cache && a.query.set("_ksTS", d.now() + "_" + d.guid()));
        return b
    }

我感到不明白的地方是第四行 delete b.context;这行代码的意义是什么呢？

删除b对像中的context属性，js的用法，有点意思。有用采纳一下