AJAX问题处理响应数据用于显示

I'm working on a project at the moment and was trying to use some AJAX to make submitting some smaller forms more smooth. I tried testing it by getting the "submit" button to just display text from a .txt file in a paragraph underneath it but that didn't work...

Here's my code:

<div style="color: #818181; width: auto; height 50vh; display:flex; flex-direction: row; justify-content: space-around;">

<div style="padding: 2vw; width: 35vw; height: 50vh; display: flex; justify-content: top; flex-direction: column; ">
<h2 style="color: #818181; margin: 0;">Contact</h2>
Questions? Go ahead.
<form method="post">
<p><input name='lcontactname' type="text" placeholder="Name" style="height: 5vh; width:28vw" required></p>
<p><input name='lcontactemail' type="text" placeholder="Email" style="height: 5vh; width:28vw" required></p>
<p><input name='lcontactsubject' type="text" placeholder="Subject" style="height: 5vh; width:28vw" required></p>
<p><input name='lcontactmessage' type="text" placeholder="Message" style="height: 5vh; width:28vw" required></p>
<p><input onClick='submitlContact' type='button' value='send' style="height: 5vh; width: 28vw; color: white;background-color:black; border: 2px white; padding: auto; font-size: calc(1vw + 0.5vh);" onClick='lcontactSend();'></p>
<p id='testpar'></p>
</form>
</div>

<script>
function submitlContact(){ //AJAX TO SUBMIT THIS FORM
    //if (window.XMLHttpRequest) {
    // code for modern browsers
    xhttp = new XMLHttpRequest();
    //} else {
    // code for IE6, IE5
   // xhttp = new ActiveXObject("Microsoft.XMLHTTP");
    //}
    xhttp.open("GET", "lcontactsubmit.txt", true);
    xhttp.send();
    document.getElementById("testpar").innerHTML = xhttp.responseText;

}   



</script>

The idea is that when the button is pressed I can see the contents of the .txt file which has a random word in called lcontactsubmit.txt and definitely is saved to contain a random jumble of letters.

Any suggestions?

:)

you have to wait for responce first, the xhttp.responseText is not available immediately after you send request, to do it use some event, for example onreadystatechange

like:

xhttp = new XMLHttpRequest();
xhttp.open("GET", "lcontactsubmit.txt", true);
xhttp.onreadystatechange = function() {
    if (this.readyState==4 && this.status==200) {
        document.getElementById("testpar").innerHTML = this.responseText;
    }
}
xhttp.send();