我想用fetch编写一个简单的基本身份验证，但我一直收到一个401错误.如果有人告诉我代码出了什么问题，那就太棒了:
let base64 = require('base-64');
let url = 'http://eu.httpbin.org/basic-auth/user/passwd';
let username = 'user';
let password = 'passwd';
let headers = new Headers();
//headers.append('Content-Type', 'text/json');
headers.append('Authorization', 'Basic' + base64.encode(username + ":" + password));
fetch(url, {method:'GET',
headers: headers,
//credentials: 'user:passwd'
})
.then(response => response.json())
.then(json => console.log(json));
//.done();