<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>JS判断上传图片格式是否正确</title>
</head>
<body>
<input type="file" id="file"/>
<input id="btn" type="button" value="button"/>
<script>
function isPicFile(fileName) {
//lastIndexOf如果没有搜索到则返回为 -1
if (fileName.lastIndexOf(".") != -1) {
var fileType = (fileName.substring(fileName.lastIndexOf(".") + 1, fileName.length)).toLowerCase();
var suppotFile = new Array();
suppotFile[0] = "jpg";
suppotFile[1] = "gif";
suppotFile[2] = "bmp";
suppotFile[3] = "png";
suppotFile[4] = "jpeg";
for ( var i = 0; i < suppotFile.length; i++) {
if (suppotFile[i] == fileType) {
return true;
} else {
continue;
}
}
alert("文件类型不合法,只能是jpg、gif、bmp、png、jpeg、png类型！");
return false;
} else {
alert("文件类型不合法,只能是 jpg、gif、bmp、png、jpeg、png类型！");
return false;
}
}
var oFile = document.getElementById('file');
var oBtn = document.getElementById('btn');
oBtn.onclick = function () {
isPicFile( oFile.value );
};
</script>
</body>
</html>