WordPress AJAX with Axios

you can use FormData

an example:

let form_data = new FormData;
form_data.append('action', 'myAction');
form_data.append('first_name', 'my first name');
form_data.append('phone', 'my phone');

axios.post(myVars.ajax_url, form_data).then(function(response){
console.log(response.data);
})