微信小程序环境下将文件上传到OSS的方法步骤

accessid= '';
accesskey= '';
host = '';

g_dirname = ''
g_object_name = ''
g_object_name_type = ''
now = timestamp = Date.parse(new Date()) / 1000; 

var policyText = {
  "expiration": "2020-01-01T12:00:00.000Z", //设置该Policy的失效时间，超过这个失效时间之后，就没有办法通过这个policy上传文件了
  "conditions": [
  ["content-length-range", 0, 1048576000] // 设置上传文件的大小限制
  ]
};

var policyBase64 = Base64.encode(JSON.stringify(policyText))
message = policyBase64
var bytes = Crypto.HMAC(Crypto.SHA1, message, accesskey, { asBytes: true }) ;
var signature = Crypto.util.bytesToBase64(bytes);

function check_object_radio() {
  var tt = document.getElementsByName('myradio');
  for (var i = 0; i < tt.length ; i++ )
  {
    if(tt[i].checked)
    {
      g_object_name_type = tt[i].value;
      break;
    }
  }
}

function get_dirname()
{
  dir = document.getElementById("dirname").value;
  if (dir != '' && dir.indexOf('/') != dir.length - 1)
  {
    dir = dir + '/'
  }
  //alert(dir)
  g_dirname = dir
}

function random_string(len) {
　　len = len || 32;
　　var chars = 'ABCDEFGHJKMNPQRSTWXYZabcdefhijkmnprstwxyz2345678';  
　　var maxPos = chars.length;
　　var pwd = '';
　　for (i = 0; i < len; i++) {
  　　pwd += chars.charAt(Math.floor(Math.random() * maxPos));
  }
  return pwd;
}

function get_suffix(filename) {
  pos = filename.lastIndexOf('.')
  suffix = ''
  if (pos != -1) {
    suffix = filename.substring(pos)
  }
  return suffix;
}

function calculate_object_name(filename)
{
  if (g_object_name_type == 'local_name')
  {
    g_object_name += "${filename}"
  }
  else if (g_object_name_type == 'random_name')
  {
    suffix = get_suffix(filename)
    g_object_name = g_dirname + random_string(10) + suffix
  }
  return ''
}

function get_uploaded_object_name(filename)
{
  if (g_object_name_type == 'local_name')
  {
    tmp_name = g_object_name
    tmp_name = tmp_name.replace("${filename}", filename);
    return tmp_name
  }
  else if(g_object_name_type == 'random_name')
  {
    return g_object_name
  }
}

function set_upload_param(up, filename, ret)
{
  g_object_name = g_dirname;
  if (filename != '') {
    suffix = get_suffix(filename)
    calculate_object_name(filename)
  }
  new_multipart_params = {
    'key' : g_object_name,
    'policy': policyBase64,
    'OSSAccessKeyId': accessid, 
    'success_action_status' : '200', //让服务端返回200,不然，默认会返回204
    'signature': signature,
  };

  up.setOption({
    'url': host,
    'multipart_params': new_multipart_params
  });

  up.start();
}

var uploader = new plupload.Uploader({
  runtimes : 'html5,flash,silverlight,html4',
  browse_button : 'selectfiles', 
  //multi_selection: false,
  container: document.getElementById('container'),
  flash_swf_url : 'lib/plupload-2.1.2/js/Moxie.swf',
  silverlight_xap_url : 'lib/plupload-2.1.2/js/Moxie.xap',
  url : 'http://oss.aliyuncs.com',

  init: {
    PostInit: function() {
      document.getElementById('ossfile').innerHTML = '';
      document.getElementById('postfiles').onclick = function() {
      set_upload_param(uploader, '', false);
      return false;
      };
    },

    FilesAdded: function(up, files) {
      plupload.each(files, function(file) {
        document.getElementById('ossfile').innerHTML += '<div id="' + file.id + '">' + file.name + ' (' + plupload.formatSize(file.size) + ')<b></b>'
        +'<div class="progress"><div class="progress-bar" style="width: 0%"></div></div>'
        +'</div>';
      });
    },

    BeforeUpload: function(up, file) {
      check_object_radio();
      get_dirname();
      set_upload_param(up, file.name, true);
    },

    UploadProgress: function(up, file) {
      var d = document.getElementById(file.id);
      d.getElementsByTagName('b')[0].innerHTML = '<span>' + file.percent + "%</span>";
      var prog = d.getElementsByTagName('div')[0];
      var progBar = prog.getElementsByTagName('div')[0]
      progBar.style.width= 2*file.percent+'px';
      progBar.setAttribute('aria-valuenow', file.percent);
    },

    FileUploaded: function(up, file, info) {
      if (info.status == 200)
      {
        document.getElementById(file.id).getElementsByTagName('b')[0].innerHTML = 'upload to oss success, object name:' + get_uploaded_object_name(file.name);
      }
      else
      {
        document.getElementById(file.id).getElementsByTagName('b')[0].innerHTML = info.response;
      } 
    },

    Error: function(up, err) {
      document.getElementById('console').appendChild(document.createTextNode("\nError xml:" + err.response));
    }
  }
});

uploader.init();

<!DOCTYPE html>
<html>
<head>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8"/>
  <title>OSS web直传</title>
  <link rel="stylesheet" type="text/css" href="style.css"/>
  <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">
</head>
<body>

<h2>OSS web直传---直接在JS签名</h2>
<ol>
<li>基于plupload封装 </li>
<li>支持html5,flash,silverlight,html4 等协议上传</li>
<li>可以运行在PC浏览器，手机浏览器，微信</li>
<li>可以选择多文件上传</li>
<li>显示上传进度条</li>
<li>可以控制上传文件的大小</li>
<li>最关键的是，让你10分钟之内就能移植到你的系统，实现以上牛逼的功能！</li>
<li>注意一点，bucket必须设置了Cors(Post打勾）,不然没有办法上传</li>
<li>注意一点，把upload.js 里面的host/accessid/accesskey改成您上传所需要的信息即可</li>
<li>此方法是直接在前端签名，有accessid/accesskey泄漏的风险, 线上生产请使用后端签名例子<a href="https://help.aliyun.com/document_detail/oss/practice/pc_web_upload/js_php_upload.html">点击查看详细文档</a></li>
</ol>
<br>
<form name=theform>
<input type="radio" name="myradio" value="local_name" checked=true/> 上传文件名字保持本地文件名字
<input type="radio" name="myradio" value="random_name" /> 上传文件名字是随机文件名
<br/>
上传到指定目录:<input type="text" id='dirname' placeholder="如果不填，默认是上传到根目录" size=50>
</form>

<h4>您所选择的文件列表：</h4>
<div id="ossfile">你的浏览器不支持flash,Silverlight或者HTML5！</div>

<br/>

<div id="container">
  <a id="selectfiles" href="javascript:void(0);" class='btn'>选择文件</a>
  <a id="postfiles" href="javascript:void(0);" class='btn'>开始上传</a>
</div>

<pre id="console"></pre>

<p>&nbsp;</p>

</body>
<script type="text/javascript" src="lib/crypto1/crypto/crypto.js"></script>
<script type="text/javascript" src="lib/crypto1/hmac/hmac.js"></script>
<script type="text/javascript" src="lib/crypto1/sha1/sha1.js"></script>
<script type="text/javascript" src="lib/base64.js"></script>
<script type="text/javascript" src="lib/plupload-2.1.2/js/plupload.full.min.js"></script>
<script type="text/javascript" src="upload.js"></script>
</html>

this.$navigate({url:"content"})

this.$parent.$navigate({url:"content"})

wepy.navigateTo({
url: '/pages/content'
})