部分安卓手机微信浏览器中使用XMLHttpRequest 2上传图片显示字节数为0的解决办法

<input type="file" id="choose" capture="camera" accept="image/*">

var filechooser = document.getElementById("choose");

filechooser.onchange = function () {
    var _this = $(this);
    if (!this.files.length) return;
    var files = Array.prototype.slice.call(this.files);
    if (files.length > 1) {
        alert("一次只能上传1张图片");
        return;
    }
    files.forEach(function (file, i) {
        if (!/\/(?:jpeg|png|gif)/i.test(file.type)) return;
        var reader = new FileReader();
        reader.onload = function () {
            var result = this.result;
            upload(result, file.type);
        };
        reader.readAsDataURL(file);
    });
};

function upload(basestr, type){
    var xhr = new XMLHttpRequest();
    var text = window.atob(basestr.split(",")[1]);
    var buffer = new Uint8Array(text.length);
    var pecent = 0;
    for (var i = 0; i < text.length; i++) {
        buffer[i] = text.charCodeAt(i);
    }
    var blob = getBlob(buffer, type);
    var formdata = new FormData();
    formdata.append('imagefile', blob);

    xhr.open('post', '/uploadtest');
    xhr.onreadystatechange = function () {
        if (xhr.readyState == 4 && xhr.status == 200) {
            var jsonData = JSON.parse(xhr.responseText);
            console.log(jsonData);
        }
    };

    //利用progress事件显示数据发送进度
    xhr.upload.addEventListener('progress', function (e) {
        pecent = ~~(100 * e.loaded / e.total) / 2;
        // 利用pecent来显示上传进度
    }, false);

    xhr.send(formdata);
}

function getBlob(buffer, format){
    var Builder = window.WebKitBlobBuilder || window.MozBlobBuilder;
    if(Builder){
        var builder = new Builder();
        builder.append(buffer);
        return builder.getBlob(format);
    } else {
        return new window.Blob([ buffer ], {type: format});
    }
}

var Q = require('q');
var fs = require('fs');
var path = require('path');
var formidable = require('formidable');
var moment = require('moment');var imageUpload = function (){ };

imageUpload.prototype.useFormParseCallback = function(req){
    var deferred = Q.defer();

    var form = new formidable.IncomingForm();
    form.parse(req, deferred.makeNodeResolver());
    return deferred.promise;
};

imageUpload.prototype.uploadImageTest = function(req){
    var pathName = 'uploadImgs/dealInfo/';
    var uploadPath = path.join(__dirname, '../../public/', pathName);

    return this.useFormParseCallback(req).then(function(files){
        var file = files[1].imagefile;
        var fileType = files[1].imagefile.type.split('/')[1];
        var newFileName = 'upload_' + moment().format('x') + Math.random().toString().substr(2, 10) + '.' + fileType;

        var readStream = fs.createReadStream(file.path);
        var writeStream = fs.createWriteStream(uploadPath + newFileName);
         
        var deferred = Q.defer();
        readStream.pipe(writeStream);
        readStream.on('end', deferred.makeNodeResolver());
        return deferred.promise.then(function() {
            fs.unlinkSync(file.path);
            return {
                fileName: newFileName,
                filePath: '/' + pathName + newFileName,
                fileSize: file.size/1024 > 1024 ? (~~(10*file.size/1024/1024))/10 + "MB" : ~~(file.size/1024) + "KB"
            };
        });
    });
};

module.exports = imageUpload;

var filechooser = document.getElementById("choose");

filechooser.onchange = function () {
    var _this = $(this);
    if (!this.files.length) return;
    var files = Array.prototype.slice.call(this.files);
    if (files.length > 1) {
        alert("一次只能上传1张图片");
        return;
    }
    files.forEach(function (file, i) {
        if (!/\/(?:jpeg|png|gif)/i.test(file.type)) return;
        var reader = new FileReader();
        reader.onload = function () {
            var result = this.result;
            upload(result, file.type);
        };
        reader.readAsDataURL(file);
    });
};

function upload(basestr, type){
    var xhr = new XMLHttpRequest();
    var text = window.atob(basestr.split(",")[1]);
    var buffer = new Uint8Array(text.length);
    var pecent = 0;
    for (var i = 0; i < text.length; i++) {
        buffer[i] = text.charCodeAt(i);
    }

    xhr.open('post', '/uploadtest?filetype=' + type.split('/')[1]);
    xhr.setRequestHeader('Content-Type', 'application/octet-stream');
    xhr.onreadystatechange = function () {
        if (xhr.readyState == 4 && xhr.status == 200) {
            var jsonData = JSON.parse(xhr.responseText);
            console.log(jsonData);
        }
    };
    //利用progress事件显示数据发送进度
    xhr.upload.addEventListener('progress', function (e) {
        pecent = ~~(100 * e.loaded / e.total) / 2;
        // 利用pecent来显示上传进度
    }, false);

    xhr.send(buffer.buffer); // 以ArrayBuffer的方式上传图片
}

imageUpload.prototype.uploadImageTest = function(req){
    var pathName = 'uploadImgs/dealInfo/';
    var uploadPath = path.join(__dirname, '../../public/', pathName);

    return this.useFormParseCallback(req).then(function(files){
        var file = files[1].file;
        var fileType = req.query.filetype ? ('.' + req.query.filetype) : '.png';
        var newFileName = 'upload_' + moment().format('x') + Math.random().toString().substr(2, 10) + '.' + fileType;

        var readStream = fs.createReadStream(file.path);
        var writeStream = fs.createWriteStream(uploadPath + newFileName);
         
        var deferred = Q.defer();
        readStream.pipe(writeStream);
        readStream.on('end', deferred.makeNodeResolver());
        return deferred.promise.then(function() {
            fs.unlinkSync(file.path);
            return {
                fileName: newFileName,
                filePath: '/' + pathName + newFileName,
                fileSize: file.size/1024 > 1024 ? (~~(10*file.size/1024/1024))/10 + "MB" : ~~(file.size/1024) + "KB"
            };
        });
    });
};