FormData的作用：
<!DOCTYPE HTML>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<form method="post" id="myForm" onsubmit="return post();">
用户名<input type="text" name="uname" />
密码<input type="password" name="upwd" />
邮箱<input type="text" name="uemail" />
<input type="submit" name="submit" value="提交" />
</form>
</body>
<script type="text/javascript">
function post() {
var myForm = document.getElementById("myForm");
//FormData既可以从表单读取数据，也可以动态append(键,值)添加
var fd = new FormData(myForm);
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function () {
if (xhr.readyState == 4) {
alert(this.responseText);
}
};
xhr.open("post", "post.php", true);
xhr.send(fd);
return false;
}
</script>
</html>
<!DOCTYPE HTML>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<form method="post" id="myForm">
<input type="file" name="file" id="upfile" />
<input type="submit" name="submit" value="提交" />
</form>
</body>
<script type="text/javascript">
var upfile = document.getElementById("upfile");
upfile.onchange = function() {
var file = this.files[0];
alert("文件名:" + file.name + "\r\n" + "大小:" + file.size + "\r\n");
};
</script>
</html>
<!DOCTYPE HTML>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<form method="post" id="myForm">
<input type="file" name="file" id="upfile" />
<input type="submit" name="submit" value="提交" />
</form>
</body>
<script type="text/javascript">
var myForm = document.getElementById("myForm");
var upfile = document.getElementById("upfile");
myForm.onsubmit = function() {
//我们创建一个FormData对象
var fd = new FormData();
var file = upfile.files[0];
//把文件添加到FormData对象中
fd.append("file", file);
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function () {
if (xhr.readyState == 4) {
alert(this.responseText);
}
};
xhr.open("post", "upfile.php", true);
//发送FormData对象
xhr.send(fd);
return false;
};
</script>
</html>
<?php
$uploadDir = ‘./upload/‘;
if(!file_exists($uploadDir)) {
@mkdir($uploadDir, 0777, true);
}
$uploadFile = $uploadDir . basename($_FILES[‘file‘][‘name‘]);
if(move_uploaded_file($_FILES[‘file‘][‘tmp_name‘], $uploadFile)) {
echo "OK";
} else {
echo "NO";
}
<!DOCTYPE HTML>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<form method="post" id="myForm">
<input type="file" name="file" id="upfile" />
<input type="submit" name="submit" value="提交" />
</form>
</body>
<script type="text/javascript">
var myForm = document.getElementById("myForm");
var upfile = document.getElementById("upfile");
upfile.onchange = function() {
//创建一个img标签
var img = document.createElement("img");
//通过file对象创建对象URL
img.src = window.URL.createObjectURL(this.files[0]);
img.height = 60;
img.onload = function() {
//释放对象URL
window.URL.revokeObjectURL(this.src);
};
document.body.appendChild(img);
};
myForm.onsubmit = function() {
//我们创建一个FormData对象
var fd = new FormData();
var file = upfile.files[0];
//把文件添加到FormData对象中
fd.append("file", file);
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function () {
if (xhr.readyState == 4) {
alert(this.responseText);
}
};
xhr.open("post", "upfile.php", true);
//发送FormData对象
xhr.send(fd);
return false;
};
</script>
</html>
php 下 html5 XHR2 + FormData + File API 上传文件
原文：http://www.cnblogs.com/jkko123/p/6352065.html