imququ.com 上找到用于 localStorage 本地保存 CSS和 JS 的实现，很简洁的实现，不过几十行的 JS 代码，特别记录一下

ls.js

(function(e, t) {
    function n(e) {
        return t.getElementById(e)
    }
    function r() {
        u("stc_nls", 1, 1)
    }
    function i(n, r) {
        var i = "";
        try {
            i = d[n] || "",
            i.length < 99 && (u(r, 0),
            t.documentElement.style.display = "none",
            c(),
            e.onbeforeunload = null,
            location.reload(!0))
        } catch (s) {
            c()
        }
        return i
    }
    function s(e, t) {
        try {
            d[e] = t,
            t !== d[e] && c()
        } catch (n) {
            c()
        }
    }
    function o(e) {
        var n = t.cookie.split("; ");
        for (var r = 0, i = n.length, s; r < i; r++) {
            s = n[r].split("=");
            if (s[0] === e)
                return s[1]
        }
        return ""
    }
    function u(e, n, r) {
        r = r || 60,
        n || (r = -1),
        r = (new Date(+(new Date) + r * 864e5)).toGMTString();
        var i = e + "=" + n + "; path=/; expires=" + r;
        location.protocol.indexOf("https") > -1 && (i += "; Secure"),
        t.cookie = i
    }
    // html2ls
    // 
    // LS.html2ls("stc_ana_js","stc_ana_js");LS.updateVersion("v", "R", "R");
    // LS.html2ls("stc_jq_js","stc_jq_js");LS.updateVersion("v", "z", "R");
    // LS.html2ls("stc_blog_js","stc_blog_js");LS.updateVersion("v", "S", "T");
    function a(e, t) {
        var r = n(t) && n(t).innerHTML.trim();
        s(e, r)
    }
    // ls2html
    // 
    // LS.ls2html("stc_ana_js","script","v")
    // LS.ls2html("stc_jq_js","script","v")
    // LS.ls2html("stc_blog_js","script","v")
    function f(n, r, s) {
        var o = i(n, s);
        if (e.execScript && r === "script")
            return e.execScript(o);
        var u = t.createElement(r);
        u.innerHTML = o,
        t.head.appendChild(u)
    }
    function c() {
        l = !0;
        var e = /(?:;)?stc_[^=]*=[^;]*;?/g
          , n = t.cookie.match(e) || []
          , r = n.length;
        while (r)
            --r,
            u(n[r].split("=")[0], 0)
    }
    // updateVersion
    function h(e, t, n) {
        if (l)
            return;
        var r = o(e).split("")
          , i = !1;
        for (var s = 0, a = r.length; s < a; s += 2)
            if (r[s] === t) {
                r[s + 1] = n,
                i = !0;
                break
            }
        i || r.push(t, n),
        u(e, r.join(""))
    }
    var l = !1, 
        p = function() {}, 
        d, 
        v = 0, 
        m = e.LS = {
            html2ls: p,
            ls2html: p,
            updateVersion: p
        };
    try {
        d = localStorage,
        m.html2ls = a,
        m.ls2html = f,
        m.updateVersion = h
    } catch (g) {
        r()
    }

})(this, document);