js原生读取json

function showJson(){
    var test;
    if(window.XMLHttpRequest){
        test = new XMLHttpRequest();
    }else if(window.ActiveXObject){
        test = new window.ActiveXObject();
    }else{
        alert("请升级至最新版本的浏览器");
    }
    if(test !=null){
        test.open("GET","points.json",true);
        test.send(null);
        test.onreadystatechange=function(){
            if(test.readyState==4&&test.status==200){
                console.log(test.responseText);
    //          var obj = JSON.parse(test.responseText);
    //          for (var name in obj){
    //              alert(obj[name].key);
    //          }
            }
        };  
 
    }
}
window.onload=function(){
  showJson();
}