细数Ajax请求中的async:false和async:true的差异

function test(){
  var temp="00";
  $.ajax({
    async: false,
    type : "GET",
    url : 'userL_checkPhone.do',
    complete: function(msg){
      alert('complete');
    },
    success : function(data) {
      alert('success');
      temp=data;
      temp="aa";
    }
  });
  alert(temp);
  }

  public void checkPhone() throws IOException {
    this.getServletResponse().setContentType("text/html; charset=UTF-8");
    this.getServletResponse().setHeader("Cache-Control", "no-cache");
    PrintWriter out = this.getServletResponse().getWriter();
    out.print("true");

  }