改造系统alert

/*************************************************************************
 * 改造系统alert
 * param  str  传入要弹出的str
 *          pos  弹出的位置        1
 *                            2
 *                            3
 * return false
 *************************************************************************/
window.alert = function (str, pos) {
    if (document.getElementById("tAlert") || !str) {
        return false;
    }
    var position = '';
    var pos = pos || 1;
    var tAlert_wrap = document.createElement("div");
    tAlert_wrap.setAttribute("id", "tAlert");
    tAlert_wrap.style.textAlign = "center";
    tAlert_wrap.style.position = "fixed";
    tAlert_wrap.style.zIndex = "100";
    switch (pos) {
        case 1:
            position = '10%';
            break;
        case 2:
            position = '40%';
            break;
        case 3:
            position = "65%";
            break;
        default:
            position = "10%";
            break;
    }
    tAlert_wrap.style.top = position;
    tAlert_wrap.style.width = "100%";
    document.getElementsByTagName("body")[0].appendChild(tAlert_wrap);
    var tAlert_in = document.createElement("div");
    tAlert_in.style.padding = "0.125rem 0.4375rem";
    tAlert_in.style.maxWidth = "6.25rem";
    tAlert_in.style.zIndex = "99";
    tAlert_in.style.fontSize = "0.375rem";
    tAlert_in.style.textShadow = "none";
    tAlert_in.style.display = "inline-block";
    tAlert_in.style.lineHeight = "0.5rem";
    tAlert_in.style.backgroundColor = "#000000";
    tAlert_in.style.color = "#ffffff";
    tAlert_in.style.borderRadius = "0.1875rem";
    tAlert_in.style.opacity = "0.8";
    tAlert_in.style.wordBreak = "break-all";
    tAlert_in.textContent = str;
    document.getElementById("tAlert").appendChild(tAlert_in);
    setTimeout(function () {
        document.getElementsByTagName("body")[0].removeChild(tAlert_wrap);
    }, 2000);
    return false;
}

牛了个逼，改造后，弹出会更美丽。弹出会自动关闭。弹出的位置可以自动调整。