以下函数从文件中读取JSON数据

function getJsonData(){
  var xhttp = new XMLHttpRequest();
  xhttp.onreadystatechange = function (){
   if(xhttp.readyState == 4 && xhttp.status == 200){
    var javaobj = JSON.parse(xhttp.response);
    return javaobj;
   }
  }
  xhttp.open("GET", "json_output.json", true)
  xhttp.send();
}

json_output.json

{"name":"John Doe","age":30,"email":"john@example.com"}