使用JavaScript FileReader实现本地图片预览

核心代码实现

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>js图片预览功能</title>
<script language=javascript>
function previewFile() {
 var preview = document.querySelector('img');
 var file  = document.querySelector('input[type=file]').files[0];
 var reader = new FileReader();
 reader.onloadend = function () {
  preview.src = reader.result;
 }
 if (file) {
  reader.readAsDataURL(file);
 } else {
  preview.src = "";
 }
}
</script>
</head>
<body>
<input type="file" onchange="previewFile()"><br>
<img src="" height="200" width="300" alt="Image preview..."/>
</body>
</html>