使用JavaScript实现alert的实例代码

<script> 
  window.alert = alert; 
  function alert(data) { 
    var MainDiv = document.createElement("div"), 
      p = document.createElement("p"), 
      AllPage = document.createElement("div"), 
      btn = document.createElement("div"), 
      textNode = document.createTextNode(data ? data : ""), 
      btnText = document.createTextNode("确定"); 
    // 控制样式 
    css(AllPage, { 
      "position": "fixed", 
      " _position": "absolute", 
      " width": "100%", 
      "height": "100%", 
      "left": "0", 
      "top": "0", 
      "background": "rgba(0, 0, 0,0.5)", 
      "-moz-opacity": "0.5", 
      "filter": "alpha(opacity=50)", 
      "z-index": "97", 
    }); 
    css(MainDiv, { 
      "position": "fixed", 
      "left": "0", 
      "right": "0", 
      "top": "30%", 
      "width": "14rem", 
      "height": "5rem", 
      "padding-top":"0.5rem", 
      "margin": "0 auto", 
      "background-color": "white", 
      "font-size": "0.75rem", 
      "text-align": "center", 
      "position": "relative", 
      "border-radius": "5px 5px 5px 5px", 
    }); 
    css(btn, { 
      "background": "#de241b", 
      "color": "white", 
      "width": "6rem", 
      "margin-left": "4rem", 
      "margin-bottom":"0.25rem", 
      "height": "1.5rem", 
      "border-radius": "5px 5px 5px 5px", 
      "position": "absolute", 
      "padding-top":"0.5rem", 
      "bottom":"0", 
    }) 
    // 内部结构套入 
    p.appendChild(textNode); 
    btn.appendChild(btnText); 
    MainDiv.appendChild(p); 
    MainDiv.appendChild(btn); 
    AllPage.appendChild(MainDiv); 
    // 整体显示到页面内 
    document.getElementsByTagName("body")[0].appendChild(AllPage); 
    //禁止滚动 
    $("body").on("touchmove", function (event) { 
      event.preventDefault; 
    }, false) 
    // 确定绑定点击事件删除标签 
    btn.onclick = function () { 
      AllPage.parentNode.removeChild(AllPage); 
      //启用滚动 
      $("body").off("touchmove"); 
    } 
  } 
  function css(targetObj, cssObj) { 
    var str = targetObj.getAttribute("style") ? targetObj.getAttribute("style") : ""; 
    for (var i in cssObj) { 
      str += i + ":" + cssObj[i] + ";"; 
    } 
    targetObj.style.cssText = str; 
  }