以下是我如何做到这一点：

HTML

<input type="file" id="file">
<button id='process-file-button'>Process</button>

JS

$('#process-file-button').on('click', function (e) {
    let files = new FormData(), // you can consider this as 'data bag'
        url = 'yourUrl';

    files.append('fileName', $('#file')[0].files[0]); // append selected file to the bag named 'file'

    $.ajax({
        type: 'post',
        url: url,
        processData: false,
        contentType: false,
        data: files,
        success: function (response) {
            console.log(response);
        },
        error: function (err) {
            console.log(err);
        }
    });
});

PHP

if (isset($_FILES) && !empty($_FILES)) {
    $file = $_FILES['fileName'];
    $name = $file['name'];
    $path = $file['tmp_name'];


    // process your file

}

您可以使用ajaxSubmit方法，如下所示：）当您选择需要上传到服务器的文件时，表单将提交到服务器：）

$(document).ready(function () {
    var options = {
    target: '#output',   // target element(s) to be updated with server response
    timeout: 30000,
    error: function (jqXHR, textStatus) {
            $('#output').html('have any error');
            return false;
        }
    },
    success: afterSuccess,  // post-submit callback
    resetForm: true
            // reset the form after successful submit
};

$('#idOfInputFile').on('change', function () {
    $('#idOfForm').ajaxSubmit(options);
    // always return false to prevent standard browser submit and page navigation
    return false;
});
});

通过ajax上传文件不再需要Iframes。我最近自己做过。查看以下页面：

使用AJAX和jQuery上传HTML5文件

http://dev.w3.org/2006/webapi/FileAPI/#FileReader-界面

更新了答案并进行了清理。使用getSize函数检查大小或使用getType函数检查类型。添加了progressbar html和css代码。

var Upload = function (file) {
    this.file = file;
};

Upload.prototype.getType = function() {
    return this.file.type;
};
Upload.prototype.getSize = function() {
    return this.file.size;
};
Upload.prototype.getName = function() {
    return this.file.name;
};
Upload.prototype.doUpload = function () {
    var that = this;
    var formData = new FormData();

    // add assoc key values, this will be posts values
    formData.append("file", this.file, this.getName());
    formData.append("upload_file", true);

    $.ajax({
        type: "POST",
        url: "script",
        xhr: function () {
            var myXhr = $.ajaxSettings.xhr();
            if (myXhr.upload) {
                myXhr.upload.addEventListener('progress', that.progressHandling, false);
            }
            return myXhr;
        },
        success: function (data) {
            // your callback here
        },
        error: function (error) {
            // handle error
        },
        async: true,
        data: formData,
        cache: false,
        contentType: false,
        processData: false,
        timeout: 60000
    });
};

Upload.prototype.progressHandling = function (event) {
    var percent = 0;
    var position = event.loaded || event.position;
    var total = event.total;
    var progress_bar_id = "#progress-wrp";
    if (event.lengthComputable) {
        percent = Math.ceil(position / total * 100);
    }
    // update progressbars classes so it fits your code
    $(progress_bar_id + " .progress-bar").css("width", +percent + "%");
    $(progress_bar_id + " .status").text(percent + "%");
};

如何使用Upload类

//Change id to your id
$("#ingredient_file").on("change", function (e) {
    var file = $(this)[0].files[0];
    var upload = new Upload(file);

    // maby check size or type here with upload.getSize() and upload.getType()

    // execute upload
    upload.doUpload();
});

Progressbar html代码

<div id="progress-wrp">
    <div class="progress-bar"></div>
    <div class="status">0%</div>
</div>

Progressbar css代码

#progress-wrp {
  border: 1px solid #0099CC;
  padding: 1px;
  position: relative;
  height: 30px;
  border-radius: 3px;
  margin: 10px;
  text-align: left;
  background: #fff;
  box-shadow: inset 1px 3px 6px rgba(0, 0, 0, 0.12);
}

#progress-wrp .progress-bar {
  height: 100%;
  border-radius: 3px;
  background-color: #f39ac7;
  width: 0;
  box-shadow: inset 1px 1px 10px rgba(0, 0, 0, 0.11);
}

#progress-wrp .status {
  top: 3px;
  left: 50%;
  position: absolute;
  display: inline-block;
  color: #000000;
}

要获取所有表单输入，包括type=“file”，需要使用FormData对象。提交表单后，您将能够在调试器->网络->标头中看到formData内容。

var url = "YOUR_URL";

var form = $('#YOUR_FORM_ID')[0];
var formData = new FormData(form);


$.ajax(url, {
    method: 'post',
    processData: false,
    contentType: false,
    data: formData
}).done(function(data){
    if (data.success){ 
        alert("Files uploaded");
    } else {
        alert("Error while uploading the files");
    }
}).fail(function(data){
    console.log(data);
    alert("Error while uploading the files");
});

我已经很晚了，但我正在寻找一个基于ajax的图像上传解决方案，我正在寻找的答案在这篇文章中有点分散。我确定的解决方案涉及FormData对象。我组装了一个基本形式的代码。您可以看到它演示了如何使用fd.append（）向表单添加自定义字段，以及如何在完成ajax请求时处理响应数据。

上传html:

<!DOCTYPE html>
<html>
<head>
    <title>Image Upload Form</title>
    <script src="//code.jquery.com/jquery-1.9.1.js"></script>
    <script type="text/javascript">
        function submitForm() {
            console.log("submit event");
            var fd = new FormData(document.getElementById("fileinfo"));
            fd.append("label", "WEBUPLOAD");
            $.ajax({
              url: "upload.php",
              type: "POST",
              data: fd,
              processData: false,  // tell jQuery not to process the data
              contentType: false   // tell jQuery not to set contentType
            }).done(function( data ) {
                console.log("PHP Output:");
                console.log( data );
            });
            return false;
        }
    </script>
</head>

<body>
    <form method="post" id="fileinfo" name="fileinfo" onsubmit="return submitForm();">
        <label>Select a file:</label><br>
        <input type="file" name="file" required />
        <input type="submit" value="Upload" />
    </form>
    <div id="output"></div>
</body>
</html>

如果您使用php，这里有一种处理上传的方法，包括使用上面html中演示的两个自定义字段。

上传.php

<?php
if ($_POST["label"]) {
    $label = $_POST["label"];
}
$allowedExts = array("gif", "jpeg", "jpg", "png");
$temp = explode(".", $_FILES["file"]["name"]);
$extension = end($temp);
if ((($_FILES["file"]["type"] == "image/gif")
|| ($_FILES["file"]["type"] == "image/jpeg")
|| ($_FILES["file"]["type"] == "image/jpg")
|| ($_FILES["file"]["type"] == "image/pjpeg")
|| ($_FILES["file"]["type"] == "image/x-png")
|| ($_FILES["file"]["type"] == "image/png"))
&& ($_FILES["file"]["size"] < 200000)
&& in_array($extension, $allowedExts)) {
    if ($_FILES["file"]["error"] > 0) {
        echo "Return Code: " . $_FILES["file"]["error"] . "<br>";
    } else {
        $filename = $label.$_FILES["file"]["name"];
        echo "Upload: " . $_FILES["file"]["name"] . "<br>";
        echo "Type: " . $_FILES["file"]["type"] . "<br>";
        echo "Size: " . ($_FILES["file"]["size"] / 1024) . " kB<br>";
        echo "Temp file: " . $_FILES["file"]["tmp_name"] . "<br>";

        if (file_exists("uploads/" . $filename)) {
            echo $filename . " already exists. ";
        } else {
            move_uploaded_file($_FILES["file"]["tmp_name"],
            "uploads/" . $filename);
            echo "Stored in: " . "uploads/" . $filename;
        }
    }
} else {
    echo "Invalid file";
}
?>

使用纯js更容易

异步函数saveFile（inp）{let formData=新formData（）；formData.append（“file”，inp.files[0]）；wait-fetch（'/upload/somedata'，｛method:“POST”，body:formData｝）；警报（“成功”）；}<input-type=“file”onchange=“saveFile（this）”>

在服务器端，您可以读取请求中自动包含的原始文件名（和其他信息）。您不需要将标题“Content-Type”设置为“multipart/form-data”。浏览器将自动设置它此解决方案应适用于所有主要浏览器。

下面是更详细的代码片段，包括错误处理、超时和额外的json发送

异步函数saveFile（inp）{让用户＝{name:'john'，年龄：34}；let formData=新formData（）；let photo=inp.files[0]；formData.append（“照片”，照片）；formData.append（“用户”，JSON.stringify（用户））；const ctrl=新建AbortController（）//超时setTimeout（（）=>ctrl.art（），50000）；尝试{let r=等待获取（'/upload/image'，｛method:“POST”，body:formData，signal:ctrl.signal｝）；console.log（'HTTP响应代码：'，r.status）；警报（“成功”）；}捕获（e）{console.log（'休斯顿我们有问题…：'，e）；}}<input-type=“file”onchange=“saveFile（this）”><br><br>在选择文件之前，打开chrome控制台>网络选项卡以查看请求详细信息。<br><br><small>因为在本例中，我们将请求发送到https://stacksnippets.net/upload/image响应代码当然是404</小>