Javascript display blank variable in html body

Question

I want to view source code of current page using Javascript, so I use this snippet code:

function getSourceCode() {
var url="http://localhost:8080/java/",xmlhttp;//Remember, same domain
if("XMLHttpRequest" in window)
    xmlhttp = new XMLHttpRequest();
if("ActiveXObject" in window)
    xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
xmlhttp.open('GET',url,true);
xmlhttp.onreadystatechange=function()
{
    if(xmlhttp.readyState==4){
        var a = xmlhttp.responseText;
        alert(a);
        document.getElementById("demo").innerHTML = a;
    }
};
xmlhttp.send(null);
}

And in HTML file, I declared a line

to print out the variable stored all source code like it alert to screen. But it always alert to my screen without print to variable "a" in the html screen.

This is my HTMl code:

<!DOCTYPE html>
<html>
<head>
    <title>Vo Tinh Thuong</title>
    <script src="code.js"></script>
</head>
<body> 
<input id="clickMe" type="button" value="clickme" onclick="getSourceCode();" />
<p id="demo"></p>
</body>
</html>

I just want to print out the variable to html webpage, not alert it like that.

I'm not able to reproduce this. When I isolate the printing part, it works — GalAbra, Feb 04 '18 at 14:19
If you click ok to alert ...it will print variable in webpage...OR comment `alert(a);` line — Sodium, Feb 04 '18 at 14:22
But in my case, when I run this code, it only alert but not print out "a" variable to web page. — Sae, Feb 04 '18 at 14:23
I just want to print all "a" variable to my screen in html webpage, not alert. — Sae, Feb 04 '18 at 14:23

Sagar Pudi · Answer 1 · 2018-02-04T14:37:50.923

0

you are sending an asynchronous request, hence it is unable to print the response. You have to keep the code in a callback and pass the response to callback from that. You can find the clean explanation in this answer (or) check this

function callBack(a){
 document.getElementById("demo").innerHTML = a;
}

call this callBack(a)

edited Feb 04 '18 at 14:37

answered Feb 04 '18 at 14:25

Sagar Pudi

4,634
3
32
51

I just added this function you said and it still can't work. – Sae Feb 04 '18 at 14:45
add after body instead of head section – Sagar Pudi Feb 04 '18 at 14:51

score 0 · Answer 2 · answered Feb 04 '18 at 15:25

0

I just solved my problem. If I want to put the "a" variable content "responseText" of source code of current page, I should put it into textarea instead p tag.

answered Feb 04 '18 at 15:25

Sae

41
8

Javascript display blank variable in html body

2 Answers2