来自axios文档:By default, axios serializes JavaScript objects to JSON. To send data in the application/x-www-form-urlencoded format instead, you can use one of the following options.

对于Nodejs，您可以使用 querystring 模块，如下所示:

For Nodejs you can use the querystring module as follows:

var querystring = require('querystring');
axios.post('http://something.com/', querystring.stringify({ foo: 'bar' }));

因此，您可以尝试data: querystring.stringify({ grant_type: 'client_credentials' })