Javascript,变量引用

Question

在类似下面的代码的情况下,您将如何访问匿名函数中的变量值？我想返回filterData的bool值(xmlhttp.responseText,thisForm); 这将是主checkAvailable函数的布尔值.提前致谢.

function checkAvailable(thisForm) {

    var xmlhttp = httpRequest();
    var isValid = true;
    var un = document.getElementById('u_username').value;
    var email = document.getElementById('u_email').value;

    xmlhttp.onreadystatechange = function(isValid) {
        if (xmlhttp.readyState == 4) {
                //I WANT TO ACCESS THIS isValid VARIABLE FROM MAIN FUNCTION checkAvailable
                isValid = filterData(xmlhttp.responseText, thisForm);
        }
    }

    xmlhttp.open("GET","profile_fetch_reg_info.php?do=available&un="+un+"&email="+email+"",true);
    xmlhttp.send(null);

    return isValid;
}

我现在的方式

function validateRegForm(thisForm) {

    var isValid = true;
    var warningIcon = "";//for later in case we want to use an icon next to warning msg

    checkAvailable(thisForm, function(isValid) { });        

    if(isValid == false)
        window.scroll(0,0);

    alert(isValid);

    return false;//isValidForm;
}


function checkAvailable(thisForm, resultFunction) {

        var xmlhttp = httpRequest();
        var un = document.getElementById('u_username').value;
        var email = document.getElementById('u_email').value;

        xmlhttp.onreadystatechange = function(isValid) {
            if(xmlhttp.readyState == 4) {
               isValid = filterData(xmlhttp.responseText, thisForm);
               resultFunction(isValid);
            }
        }
            xmlhttp.open("GET","profile_fetch_reg_info.php?do=available&un="+un+"&email="+email+"",true);
    xmlhttp.send(null);
}

Answer 1

修改checkAvailable函数以获取一个附加参数,该参数是使用结果调用的函数.

function checkAvailable(thisForm, resultFunction) {
  ..
  xmlhttp.onreadystatechange = function(isValid) {
    if (xmlhttp.readyState == 4) {
       //I WANT TO ACCESS THIS isValid VARIABLE FROM MAIN FUNCTION checkAvailable
       isValid = filterData(xmlhttp.responseText, thisForm);
       resultFunction(isValid);
    }
  }
}

然后,你可以这样称呼它:

checkAvailable(thisForm, function(isValid) { 
  // Use the isValid value which is the result of the checkAvailable call.
});

编辑 这是对您发布的修改后代码的更改.

function validateRegForm(thisForm) {
  var isValid = true;
  var warningIcon = "";//for later in case we want to use an icon next to warning msg

  checkAvailable(thisForm, function(isValid) { 
    if(isValid == false)
      window.scroll(0,0);

    alert(isValid);
  }

  // WARNING!!  This will happen before the result is discovered.
  // You'll need to modify the function that called into validateRegForm.
  // It should not wait for a return parameter either.
  return false;//isValidForm;
}