Axios post in react native throws property btoa does not exist error?

Question

when i execute axios post ,i am getting below error ,but when i add axios get , below registration process run without any issue. Any help would be highly appreciated.

LOG [ReferenceError: Property 'btoa' doesn't exist]

axios.post('https://........', {
  auth: {
    username: 'james',
    password: '123456'
  }

  }).then(function(response) {
      console.log(response);
}).catch(function(error) {
console.log(error);
});