JS实现图片上传预览功能

废话不多说了，直接给大家贴js代码了，具体代码如下所示：

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
  <title></title>
</head>
<body>
  <div id="divPreview">
    <img id="imgHeadPhoto" src="noperson.jpg" style="width: 160px; height: 170px; border: solid 1px #d2e2e2;"
      alt="" />
  </div>
  <input type="file" onchange="PreviewImage(this,'imgHeadPhoto','divPreview');" size="20" />
  <script type="text/javascript">
    //js本地图片预览，兼容ie[6-9]、火狐、Chrome17+、Opera11+、Maxthon3
    function PreviewImage(fileObj, imgPreviewId, divPreviewId) {
      var allowExtention = ".jpg,.bmp,.gif,.png"; //允许上传文件的后缀名document.getElementById("hfAllowPicSuffix").value;
      var extention = fileObj.value.substring(fileObj.value.lastIndexOf(".") + 1).toLowerCase();
      var browserVersion = window.navigator.userAgent.toUpperCase();
      if (allowExtention.indexOf(extention) > -1) {
        if (fileObj.files) {//HTML5实现预览，兼容chrome、火狐7+等
          if (window.FileReader) {
            var reader = new FileReader();
            reader.onload = function (e) {
              document.getElementById(imgPreviewId).setAttribute("src", e.target.result);
            }
            reader.readAsDataURL(fileObj.files[0]);
          } else if (browserVersion.indexOf("SAFARI") > -1) {
            alert("不支持Safari6.0以下浏览器的图片预览!");
          }
        } else if (browserVersion.indexOf("MSIE") > -1) {
          if (browserVersion.indexOf("MSIE 6") > -1) {//ie6
            document.getElementById(imgPreviewId).setAttribute("src", fileObj.value);
          } else {//ie[7-9]
            fileObj.select();
            if (browserVersion.indexOf("MSIE 9") > -1)
              fileObj.blur(); //不加上document.selection.createRange().text在ie9会拒绝访问
            var newPreview = document.getElementById(divPreviewId + "New");
            if (newPreview == null) {
              newPreview = document.createElement("div");
              newPreview.setAttribute("id", divPreviewId + "New");
              newPreview.style.width = document.getElementById(imgPreviewId).width + "px";
              newPreview.style.height = document.getElementById(imgPreviewId).height + "px";
              newPreview.style.border = "solid 1px #d2e2e2";
            }
            newPreview.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod='scale',src='" + document.selection.createRange().text + "')";
            var tempDivPreview = document.getElementById(divPreviewId);
            tempDivPreview.parentNode.insertBefore(newPreview, tempDivPreview);
            tempDivPreview.style.display = "none";
          }
        } else if (browserVersion.indexOf("FIREFOX") > -1) {//firefox
          var firefoxVersion = parseFloat(browserVersion.toLowerCase().match(/firefox\/([\d.]+)/)[1]);
          if (firefoxVersion < 7) {//firefox7以下版本
            document.getElementById(imgPreviewId).setAttribute("src", fileObj.files[0].getAsDataURL());
          } else {//firefox7.0+
            document.getElementById(imgPreviewId).setAttribute("src", window.URL.createObjectURL(fileObj.files[0]));
          }
        } else {
          document.getElementById(imgPreviewId).setAttribute("src", fileObj.value);
        }
      } else {
        alert("仅支持" + allowExtention + "为后缀名的文件!");
        fileObj.value = ""; //清空选中文件
        if (browserVersion.indexOf("MSIE") > -1) {
          fileObj.select();
          document.selection.clear();
        }
        fileObj.outerHTML = fileObj.outerHTML;
      }
      return fileObj.value;  //返回路径
    }
  </script>
</body>
</html>

以上所述是小编给大家介绍的JS实现图片上传预览功能，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对我们网站的支持！