我想从文件浏览器对话框上传图片。我希望在用户选择图片时预览图片。它在jsfiddle中工作,但它在我的项目中不起作用。
错误是
“未捕获的TypeError:无法读取属性'addEventListener'的null”
我不知道如何解决它。请帮帮我?
function handleFileSelect(evt) {
var files = evt.target.files; // FileList object
// Loop through the FileList and render image files as thumbnails.
for (var i = 0, f; f = files[i]; i++) {
// Only process image files.
if (!f.type.match('image.*')) {
continue;
}
var reader = new FileReader();
// Closure to capture the file information.
reader.onload = (function(theFile) {
return function(e) {
// Render thumbnail.
var span = document.createElement('span');
span.innerHTML = ['<img class="thumb" src="', e.target.result,
'" title="', escape(theFile.name), '"/>'
].join('');
document.getElementById('previewImg').insertBefore(span, null);
};
})(f);
// Read in the image file as a data URL.
reader.readAsDataURL(f);
}
}
document.getElementById('files').addEventListener('change', handleFileSelect, false);
.thumb {
border: 1px solid #000000;
height: 75px;
margin: 10px 5px 0 0;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type='file' id="files" name="image" multiple="multiple" />
<div id='previewImg'></div>
答案 0 :(得分:0)
我假设您的document.getElementById ('files')
命令在页面完全呈现之前正在运行,因此选择器无法在页面上找到任何元素,并且您无法将addEventListener
添加到任何元素。
您必须将选择器放在文档加载函数中,如下所示:
document.addEventListener('DOMContentLoaded', function(){
document.getElementById('files').addEventListener('change', handleFileSelect, false);
}, false);