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Editorial Team
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Asked: 2026-05-27T01:21:55+00:00

I’m trying to make a webpage change the background color every one second using

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I’m trying to make a webpage change the background color every one second using JavaScript.
I’m using setTimeout but I can’t figure out how to get my variable to change in the function. Here’s my code:

 <!DOCTYPE html>
 <html>
     <head>
         <script type="text/javascript">
         function changecolors() {
             x = 1; // <-- I know this is wrong, I just don't know where to place it 
             var t = setTimeout("change()", 1000);
         }
         function change() {
             while(x < 3) {
                 if(x = 1) {
                     color = "red";
                     x++;
                 } else if (x = 2) {
                     color = "green";
                     x = 1;
                 }
                 document.body.style.background = color;
             }
         }
     </head>
     <body onload="changecolors()">
     </body>
 </html>
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1 Answer

  1. Editorial Team

    There are several problems here. I’ll just fix your code:

    var x;

function changecolors() {
    x = 1;
    setInterval(change, 1000);
}

function change() {
    if (x === 1) {
        color = "red";
        x = 2;
    } else {
        color = "green";
        x = 1;
    }

    document.body.style.background = color;
}

    Basically…

    • You need setInterval instead of setTimeout. setTimeout only executes once.
    • = assigns, even in an if statement. You need == (or better, ===).
    • You shouldn’t pass a string to setTimeout or setInterval. Instead, pass a function.

    Another point of note: you shouldn’t use the on* attributes of HTML elements for event listeners, but especially not on <body>, since you can do this in JavaScript instead, and be unobtrusive:

    window.onload = changecolors;

    Of course, you could do it with fewer functions and no pollution of the global namespace.

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