Executing JavaScript in Shared Hosting (cPanel) Using PHP

In some cPanel environments where your website is hosted on shared hosting, it can be very difficult to find a way to evaluate JavaScript. In this post, I’ll share a method I discovered that allows you to execute JS on a shared host directly from PHP code.

The command you are looking for is js.

If you run js -v in the terminal from cpanel dashboard, you’ll see this output:

$ js -v
JavaScript-C 1.8.5 2011-03-31
usage: js [options] [scriptfile] [scriptarg...]
Options:
...

Even if the cPanel admin doesn’t allow you to install Node.js or another JS engine, the js command is usually available.

The command is very limited—it doesn’t support modern JavaScript syntax. It appears to be based on an older version of JavaScript (likely ES5 or earlier). For example:

• Missing string.replaceAll()
• No console.log()
• No support for async functions

To work around this, you’ll need to:

1. Manually implement missing features.
2. Rewrite parts of your code to be compatible.

The biggest challenge is retrieving the output of your JS code. Since console.log() doesn’t work, I found an unconventional solution: throwing an error with the result.

When you throw an error, it prints to the console, and you can capture it from PHP.

Here’s a working example:

function executeJs($jsCode) {
    // Add missing functionality
    $replaceAllString = "
        String.prototype.replaceAll = function(match, replace) {
            return this.replace(new RegExp(match, 'g'), function() { return replace });
        }
    ";

    // Combine with user's JS code
    $jsCode = $replaceAllString . $jsCode;

    // Create a temporary file
    $tempFile = tmpfile();
    $metaData = stream_get_meta_data($tempFile);
    $tmpFilename = $metaData['uri'];
    fwrite($tempFile, $jsCode);

    // Execute JS and capture output
    $cmd = "/bin/js -f " . escapeshellarg($tmpFilename) . " 2>&1";
    $result = shell_exec($cmd);

    // Clean up the output
    $result = str_replace("uncaught exception: ", "", $result);
    return trim($result);
}

This method isn’t perfect, but it’s a useful workaround when you’re restricted to shared hosting.