symmetricScroller

by ethertank

HTML

<pre class="scroller">Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
</pre>

<pre class="scroller">Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
</pre>

<div class="scroller">Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
    Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
    Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
    Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
</div>

<pre>この子は横にもリサイズ可能。
固定サイズのdivでラッピングとかしてないから。</pre>

CSS

body { background-color: #DDDDDD; font: 13px sans-serif; }

pre {
    overflow-x: auto;
    border: 1px solid #000;
    outline: 1px solid #fff;
    background: #fff;
    padding: 10px;
    box-shadow: inset 1px 1px 3px 0 #99a;
    resize: both;
    width: 200px;
    min-width: 100px; /*       */
    max-width: 90%;
}

.scroller_wrapper { background: red; }

JavaScript

//※関数
var symmetricScroller = function() {
    var doc = document;
    window.addEventListener("load", function() {
        var targets = doc.getElementsByClassName('scroller'),
            wrapper = [],
            bar = [],
            pad = [];

        for (var i = 0; i < targets.length; i++) {
            if (targets[i].scrollWidth > targets[i].offsetWidth) {
                wrapper[i] = doc.createElement("div");
                bar[i] = doc.createElement("div");
                pad[i] = doc.createElement("div");

                wrapper[i].appendChild(targets[i].cloneNode(true));
                wrapper[i].className = "scroller_wrapper";
                targets[i].parentNode.replaceChild(wrapper[i], targets[i]);
                wrapper[i].appendChild(targets[i]);

                wrapper[i].style.position = "relative";
                wrapper[i].style.margin = "0";
                wrapper[i].style.padding = "0";

                pad[i].style.width = targets[i].scrollWidth + "px";
                pad[i].style.height = "1px"; //A 高さが無いとバーが出ん
                //pad[i].innerHTML = "&nbsp;"; //B
                bar[i].appendChild(pad[i]);

                bar[i].style.width = targets[i].clientWidth; //A
                //bar[i].style.width = targets[i].offsetWidth; //B

                bar[i].style.height =
                    targets[i].offsetHeight - 
                    targets[i].clientHeight - 
                    targets[i].style.borderTop - 
                    targets[i].style.borderBottom -
                    2 + "px"; //※この 2px は何
                
                bar[i].style.overflowX = "scroll"; //※
                wrapper[i].style.marginTop = targets[i].style.marginTop;
                targets[i].style.marginTop = "0"; //対象要素の上部マージンをラッパー側に移植。
                wrapper[i].insertBefore(bar[i], targets[i]);
                
               
            } //endif
        } //endfor
        
        
            //for文で回してもうまい事いかんのは何で？
           ...