Display data-attribute with corresponding classname

show-data.js

(function() {
    var O,N,M,K,J,I,H,G,F,E,D,C,B,A,L;
    M = "ref";
    C = "number";
    E = "." + M + ":before{";
    E += "display:inline-block;";
    E += "position:absolute;";
    E += "padding:2px;";
    E += "color:white;";
    E += "background-color:black;";
    E += "font-weight:bold;";
    E += "}";
    D = 1000;
    A = "not found.";
    O = document;
    N = function(P) { return O.getElementsByClassName(P); };
    K = K = O.createElement("style");
    J = O.getElementsByTagName("head")[0];
    I = N(M);
    H = I.length;
    for (F = 0; F < H; F++) {
        G = I[F];
        B = G.id || M + D;
        G.id = B;
        E += "#" + B + ':before{content:"' + G.getAttribute("data-" + C) + '";';
        E += "z-index:" + D+++";";
        E += "}";
    }
    if (H) {
        K.appendChild(O.createTextNode(E));
        J.appendChild(K);
        console.log(I);
    } else { console.log(M + " " + A); }
} ());