www.1688.com首页的这段JS代码是干嘛用的？

Question

    (function(a) {
    function B(a, b) {
        if (a.nodeName === "IMG") {
            D(a, b);
            return
        }
        a.nodeName === "SCRIPT" ? E(a, b) : F(a, b)
    }
    function C(a) {
        o ? a.removeNode() : a && a.parentNode && a.parentNode.removeChild(a),
        a = undefined
    }
    function D(a, b) {
        a.onload = a.onerror = function() {
            a.onload = a.onerror = null,
            C(a),
            b()
        }
    }
    function E(a, b) {
        a.onload = a.onerror = a.onreadystatechange = function() {
            t.test(a.readyState) && (a.onload = a.onerror = a.onreadystatechange = null, C(a), b())
        }
    }
    function F(a, b) {
        e || f ? setTimeout(function() {
            G(a, b)
        },
        1) : a.onload = a.onerror = function() {
            a.onload = a.onerror = null,
            a = undefined,
            b()
        }
    }
    function G(a, b) {
        var c;
        if (e) a.sheet && (c = !0);
        else if (a.sheet) try {
            a.sheet.cssRules && (c = !0)
        } catch(d) {
            d.name === "NS_ERROR_DOM_SECURITY_ERR" && (c = !0)
        }
        setTimeout(function() {
            c ? b() : G(a, b)
        },
        1)
    }
    function H() {}
    function I() {
        var a, d, e, f, g;
        if (document.currentScript) return document.currentScript;
        if (document.attachEvent) {
            if (b) return b;
            if (c && c.readyState === "interactive") return c;
            a = n.getElementsByTagName("script");
            for (d = 0; d < a.length; d++) {
                e = a[d];
                if (e.readyState === "interactive") return c = e,
                e
            }
        } else {
            try {
                makeReferenceError
            } catch(g) {
                f = g.stack
            }
            if (!f) return undefined;
            g = f.indexOf(" at ") !== -1 ? " at ": "@";
            while (f.indexOf(g) !== -1) f = f.substring(f.indexOf(g) + g.length);
            f = f.replace(/:\d+:\d+$/ig, ""),
            a = document.getElementsByTagName("script");
            for (d = a.length - 1; d > -1; d--) if (a[d].src === f) return a[d]
        }
    }
    function J() {
        var a = I();
        return a ? a.hasAttribute ? a.src: a.getAttribute("src", 4) : ""
    }
    function K(b) {
        var c = !1,
        d = !0,
        e = a.document,
        f = e.documentElement,
        g = e.addEventListener ? "addEventListener": "attachEvent",
        h = e.addEventListener ? "removeEventListener": "detachEvent",
        i = e.addEventListener ? "": "on",
        j = function(d) {
            if (d.type == "readystatechange" && e.readyState != "complete") return; (d.type == "load" ? a: e)[h](i + d.type, j, !1),
            !c && (c = !0) && b.call(a, d.type || d)
        },
        k = function() {
            try {
                f.doScroll("left")
            } catch(a) {
                setTimeout(k, 50);
                return
            }
            j("poll")
        };
        if (e.readyState == "complete") b.call(a, "lazy");
        else {
            if (e.createEventObject && f.doScroll) {
                try {
                    d = !a.frameElement
                } catch(l) {}
                d && k()
            }
            e[g](i + "DOMContentLoaded", j, !1),
            e[g](i + "readystatechange", j, !1),
            a[g](i + "load", j, !1)
        }
    }
    function L() {
        var a, b = 0;
        if (h.length) for (; a = h[b++];) a()
    }
    var b, c, d, e, f, g, h, i, j, k, l, m = document,
    n = m.head || m.getElementsByTagName("head")[0] || m.documentElement,
    o = !1,
    p = n.getElementsByTagName("base")[0],
    q = /\.jpg|jpeg|png|gif|bmp(?:\?|$)/i,
    r = /\.css(?:\?|$)/i,
    s = /\.js(?:\?|$)/i,
    t = /loaded|complete|undefined/,
    u = m.createElement("script").async === !0 || "MozAppearance" in m.documentElement.style || window.opera,
    v = Array.prototype,
    w = Object.prototype.toString,
    x = function(a) {
        return w.call(a) === "[object Function]"
    },
    y = function(a) {
        return w.call(a) === "[object String]"
    },
    z = function(a) {
        return w.call(a) === "[object Array]"
    },
    A = function(a, c, d, e, f) {
        var g = r.test(a),
        h = q.test(a),
        i = h ? new Image: document.createElement(g ? "link": "script");
        if (s.test(a) && d) {
            var j = x(d) ? d(a) : d;
            j && (i.charset = j)
        }
        B(i, c || H);
        if (h) {
            i.src = a;
            return
        }
        g ? (i.rel = "stylesheet", i.href = a) : (i.async = e ? "async": !1, i.type = "text/" + (f || "javascript"), i.src = a),
        b = i,
        p ? n.insertBefore(i, p) : n.appendChild(i),
        b = null
    };
    d = navigator.userAgent,
    e = Number(d.replace(/.*AppleWebKit\/(\d+)\..*/, "$1")) < 536,
    f = d.indexOf("Firefox") > 0 && !("onload" in document.createElement("link")),
    g = [],
    h = [],
    i = {},
    j = {
        charset: "gbk",
        type: "order"
    },
    k = function(a, b) {
        var c = arguments,
        d = g.length,
        e = d - 1,
        f = g[e],
        h = j.charset,
        k = I(),
        l,
        m = function(a) {
            if (d == 0) {
                a();
                return
            }
            if (J()) {
                a();
                return
            }
            if (f) {
                f.loaded ? a() : f.callChain.push(a);
                return
            }
            a()
        };
        if (!x(a) && !y(a)) return;
        if (x(a)) {
            b = a,
            m(b);
            return
        }
        b || (b = H);
        if (c.length === 1) return i[a] && i[a].exports;
        i[a] = {
            init: function() {
                var c = i[a].exports;
                return b(c),
                c
            },
            exports: {}
        },
        l = i[a].init,
        m(l)
    },
    l = function(b) {
        var c = b.callChain,
        d = c.length;
        for (var e = 0; e < d; e++) c[e].call(a);
        b.called = !0
    },
    k.executeOrder = function(a, b) {
        var c, d = j.charset,
        e = function() {
            var a = g[c],
            b = g.length,
            f = g[c - 1],
            h = g[c + 1];
            a.loaded = !0,
            l(a);
            if (h && h.preloaded) {
                c++,
                A(h.url, e, d);
                return
            }
        },
        f = function() {
            A(a,
            function() {
                var b = g[c],
                f = g.length,
                h = g[c - 1];
                b.preloaded = !0,
                (c == 0 || h && h.called) && A(a, e, d)
            },
            j.charset, null, "cache")
        };
        g.push({
            url: a,
            callChain: [b],
            perloaded: !1,
            loaded: !1,
            called: !1
        }),
        c = g.length - 1,
        u ? A(a,
        function() {
            l(g[c])
        },
        j.charset) : f()
    },
    k.executeNow = function(a, b) {
        A(a, b, j.charset, !0)
    },
    k.load = function(b, c, d) {
        var e;
        return y(c) && (d = c, c = H),
        arguments.length == 1 && (c = H),
        d = s.test(b) ? d || j.type: "now",
        e = "execute" + d.charAt(0).toUpperCase() + d.substring(1),
        k[e] && k[e].call(a, b, c, j.charset)
    },
    k.ready = function(a, b) {
        x(a) && arguments.length == 1 && (b = a),
        h.push(function() {
            k(a, b)
        })
    },
    k.clean = function() {
        g = [],
        i = [],
        h = []
    },
    K(function() {
        L()
    }),
    k.modules = i,
    k.config = j,
    a.pump = k
})(window);

Answer 1

看到第100行，以及各种script，各种图片脚本和CSS的后缀，以及各种异步事件，有理由相信这段代码是用来做lazyload的，当然本人仅仅是猜测，也可能不仅仅是干这个的或者是基本上不干这个的。