从ajax响应运行Javascript脚本

Question

I want to call a JS Script in Ajax response. What it does is pass the document.getElementById script to the Ajax responseText.

The current code returns me this error: Uncaught TypeError: Cannot set property 'innerHTML' of null

This is done with Visual Studio Cordova..

Ajax:

$("#loginBtn").click(function() {
    var username = document.getElementById("username").value;
    var password = document.getElementById("password").value;
    var xmlhttp = new XMLHttpRequest();
    xmlhttp.onreadystatechange = function () {
        if (this.readyState == 4 && this.status == 200) {
            document.write(this.responseText);
        }
    }
    xmlhttp.open("POST", "http://www.sampleee.esy.es/login.php", true);
    xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    xmlhttp.send("username=" + username + "&" + "password=" + password);
});

PHP:

if($count == 1){
   echo "document.getElementById('alertBox').innerHTML = 'Login Success!';
        document.getElementById('alertBox').className = 'alert alert-success';
        document.getElementById('alertBox').style.display = 'block';
        setTimeout(function () {
                window.location.href = '../html/dashboard.html';
            }, 1000);
        ";
}else{
       echo "document.getElementById('alertBox').innerHTML = 'Invalid login details'; 
        document.getElementById('alertBox').className = 'alert alert-danger';
        document.getElementById('alertBox').style.display = 'block';
        ";
}

Answer 1

You can solve it by change a small ,just you have to write js code on ajax success that you write in php page.on the php page there are no alertBox element thats why the error occured.

Your Js code will be like this:-

$("#loginBtn").click(function() {
var username = document.getElementById("username").value;
var password = document.getElementById("password").value;
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function () {
    if (this.readyState == 4 && this.status == 200) {
        if(this.responseText=="success"){
        document.getElementById('alertBox').innerHTML = 'Login Success!';
        document.getElementById('alertBox').className = 'alert alert-success';
        document.getElementById('alertBox').style.display = 'block';
        setTimeout(function () {
        window.location.href = '../html/dashboard.html';
        }, 1000);
        }elseif(this.responseText=="error"){
         document.getElementById('alertBox').innerHTML = 'Invalid login details'; 
    document.getElementById('alertBox').className = 'alert alert-danger';
    document.getElementById('alertBox').style.display = 'block'
         }
    }
}
xmlhttp.open("POST", "http://www.sampleee.esy.es/login.php", true);
xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xmlhttp.send("username=" + username + "&" + "password=" + password);
  });

And php code like:-

 if($count == 1){
 echo "success";
 }else{
   echo "error";
  }