ASP 怎么使用七牛上传单个文件，

我现在用JS做的上传，老是出现{"error":"token not specified"}

accessKey和secretKey是在函数外赋值
function getUpToken(filename,deadline){
var putpolicy='{
"scope":"launch1080x1920.png",
"deadline":'+deadline+',
"returnBody":
"{

\"name\":$(fname),
\"size\":$(fsize),
\"w\":$(imageInfo.width),
\"h\":$(imageInfo.height),
\"hash\":$(etag)

}"
}';

var encoded=base64encode(utf16to8(putpolicy));
var hash=CryptoJS.HmacSHA1(encoded,secretKey);
var encoded_signed=hash.toString(CryptoJS.enc.Base64);
var upload_token=accessKey + ":" + safe64(encoded_signed) + ":" + encoded;
return upload_token;

}