由于web开发需要，需要在用户在web界面从本地选择文件（图像），选择完成之后，在html5界面中显示（预览），下面介绍如何用JavaScript来实现
1、前端html代码
使用bootstrap前端框架
<!doctype html>
<html lang="en">
<head>
<!-- Required meta tags -->
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<!-- Bootstrap CSS -->
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@4.4.1/dist/css/bootstrap.min.css" integrity="sha384-Vkoo8x4CGsO3+Hhxv8T/Q5PaXtkKtu6ug5TOeNV6gBiFeWPGFN9MuhOf23Q9Ifjh" crossorigin="anonymous">
<title>图片预览测试</title>
</head>
<body>
<div class="container mt-3">
<div class="container">
<form>
<div class="form-group">
<label for="exampleFormControlFile1" style="font-size: 30px;">请选择图片</label>
<div class="row">
<div class="col-6">
<!-- 用户完成选择文件，就会触发js中fileSelected()的函数代码，从而实现图像预览 -->
<input type="file" id="exampleFormControlFile" name="file" style="width: 200px;" onchange="fileSelected()">
<button type="button" class="btn btn-primary" id="button-submit">确认</button>
</div>
<div class="col-6">
</div>
</div>
</div>
</form>
</div>
<div class="container">
<div class="row">
<!-- 需要预览的图片显示区 -->
<div class="col-8"><img id="preview" width="600" ></div>
<div class="col-4">
</div>
</div>
</div>
</div>
<script src="https://cdn.staticfile.org/jquery/1.10.2/jquery.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.0/dist/umd/popper.min.js" integrity="sha384-Q6E9RHvbIyZFJoft+2mJbHaEWldlvI9IOYy5n3zV9zzTtmI3UksdQRVvoxMfooAo" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap@4.4.1/dist/js/bootstrap.min.js" integrity="sha384-wfSDF2E50Y2D1uUdj0O3uMBJnjuUD4Ih7YwaYd1iqfktj0Uod8GCExl3Og8ifwB6" crossorigin="anonymous"></script>
</body>
</html>
2、JS代码
这个js代码放在body中
<script>
function fileSelected(){
// 这个地方通过id号获取输入文件对象
var oFile = document.getElementById('exampleFormControlFile').files[0];
// 通过id号获取预览的图像显示区
var oImage = document.getElementById('preview');
// prepare HTML5 FileReader
var oReader = new FileReader();
oReader.onload = function(e){
oImage.src = e.target.result;
oImage.onload = function (){
// do no thing
};
};
// read selected file as DataURL
oReader.readAsDataURL(oFile);
}
</script>
3、测试
效果
0