XMLHttpResquest

var request = new XMLHttpRequest();
request.open('GET', url);
request.responseType = 'text'; # text, json
request.onload = function(){
    para.textContent = request.response; // update content
}
request.send();

Fetch API

fetch(url).then(function(response){
    response.text().then(function(text){
        para.textContent = text; // update content
    });
});

github 完整代码