为调试JavaScript添加输出窗口

调试JavaScript是一件很麻烦的事，尽管有很多很好用的调试工具，但有时候想要跟踪值的变化，但即不想中断脚本执行，也不想用alert显示值信息，这种情况下，一般的做法是在页面上添加一个DIV或者其它元素，然后再往里面添加调试信息。虽然不是很复杂的实现，但每次都要这样就会很麻烦，所以我写了一小段脚本，用来自动生成这个输出窗口。

window.Babu = {};

Babu.Debugging = {};

Babu.Debugging.writeLine = function(format, arg1, arg2) {

    var console = Babu.Debugging._getConsole();

    if (console.get_visible()) {
        var msg = format;

        if (typeof msg !== "undefined" && msg !== null) {
            var index;
            if (typeof msg === "string") {
                var array = format.match(/\{(\d+)\}/g);
                if (array) {
                    for (var i = 0; i < array.length; i++) {
                        index = array[i];
                        index = parseInt(index.substr(1, index.length - 2)) + 1;
                        msg = msg.replace(array[i], arguments[index]);
                    }
                }
            }
        }

        var span = document.createElement("SPAN");
        span.appendChild(document.createTextNode(msg));
        console._output.appendChild(span);
        console._output.appendChild(document.createElement("BR"));
        span.scrollIntoView();

        return span;
    }
}

Babu.Debugging._getConsole = function() {
    var console = Babu.Debugging._console;

    if (!console) {
        var div = document.createElement("DIV");
        div.style.position = "fixed";
        div.style.right = "3px";
        div.style.bottom = "3px";
        div.style.width = "350px";
        div.style.height = "180px";
        div.style.backgroundColor = "white";
        div.style.color = "black";
        div.style.border = "solid 2px #afafaf";
        div.style.fontSize = "12px";

        document.body.appendChild(div);

        Babu.Debugging._console = console = div;

        div = document.createElement("DIV");
        div.style.backgroundColor = "#e0e0e0";
        div.style.position = "absolute";
        div.style.left = "0px";
        div.style.right = "0px";
        div.style.top = "0px";
        div.style.height = "16px";
        div.style.padding = "2px 2px";
        div.style.margin = "0px";
        console.appendChild(div);
        console._toolbar = div;

        div = document.createElement("DIV");
        div.style.overflow = "auto";
        div.style.whiteSpace = "nowrap";
        div.style.position = "absolute";
        div.style.left = "0px";
        div.style.right = "0px";
        div.style.top = "20px";
        div.style.bottom = "0px";
        div.style.height = "auto";
        console.appendChild(div);
        console._output = div;

        var btn;

        btn = document.createElement("SPAN");
        btn.innerHTML = "收缩";
        btn.style.margin = "0px 3px";
        btn.style.cursor = "pointer";
        console._toolbar.appendChild(btn);
        btn.onclick = function() { if (console.get_collapsed()) console.expand(); else console.collapse(); }

        btn = document.createElement("SPAN");
        btn.innerHTML = "清除";
        btn.style.margin = "0px 3px";
        btn.style.cursor = "pointer";
        console._toolbar.appendChild(btn);
        btn.onclick = Babu.Debugging.clearConsole;

        btn = document.createElement("SPAN");
        btn.innerHTML = "关闭";
        btn.style.cursor = "pointer";
        btn.style.margin = "0px 3px";
        console._toolbar.appendChild(btn);
        btn.onclick = function() { Babu.Debugging.hideConsole(); }

        console.get_visible = function() { return this.style.display !== "none" };
        console.get_collapsed = function() { return !(!this._collapseState) };

        console.collapse = function() {
            if (!this.get_collapsed()) {
                this._output.style.display = "none";
                this._toolbar.childNodes[1].style.display = "none";
                this._toolbar.childNodes[2].style.display = "none";
                this._toolbar.childNodes[0].innerHTML = "展开";
                this._collapseState = {  this.style.width, height: this.style.height }
                this.style.width = "30px";
                this.style.height = "16px";
            }
        }

        console.expand = function() {
            if (this.get_collapsed()) {
                this._output.style.display = "";
                this._toolbar.childNodes[1].style.display = "";
                this._toolbar.childNodes[2].style.display = "";
                this._toolbar.childNodes[0].innerHTML = "收缩";
                this.style.width = this._collapseState.width;
                this.style.height = this._collapseState.height;
                this._collapseState = null;

            }
        }
    }

    return console;
}

Babu.Debugging.showConsole = function() {
    Babu.Debugging._getConsole().style.display = "";
}

Babu.Debugging.hideConsole = function() {
    var console = Babu.Debugging._console;

    if (console) {
        console.style.display = "none";
    }
}

Babu.Debugging.clearConsole = function() {
    var console = Babu.Debugging._console;
    if (console) console._output.innerHTML = "";
}

调用方法很简单：

Babu.Debugging.writeLine("调试信息");

Babu.Debugging.writeLine("带参数的调试信息：参数1={0}，参数2={1}", arg1, arg2);

调用之后，会自动在窗口的右下角出现一个固定位置的窗口，并显示相应的内容。效果图请看下面：

最后补充一点，因为IE6不支持position: fixed，因此显示的时候会乱七八糟。