CODEWITHSUNDEEP
javascriptphpjquerydynamic
Guns
Guns

Reputation: 2728

Dynamically creating and loading JS

I am working on a PHP project which writes js files and executes them on page load.

Is it a good practice to write JS file dynamically and append the script tag to the page html and execute it only every page request?

Here is my working creating and linking the JS File:

<?php

if (!function_exists('setScript')) {
    function setScript($script = null)
    {
        static $_script = array();
        if ($script == null) {
            return $_script;
            $_script = array();
        } else {
            $_script[] = $script;
        }
    }
}

if (!function_exists('linkJs')) {
    function linkJs($controllerName, $actionName)
    {
        $jsFileName = randomString(40) . '.js';
        $folderName = PUBLIC_DIR . DS . 'generated';
        if (!is_dir($folderName)) {
            mkdir($folderName);
            chmod($folderName, 777);
        }
        $fileName = $folderName . DS . $jsFileName;
        $availableFiles = scandir($folderName);
        unset($availableFiles[0]);
        unset($availableFiles[1]);
        foreach ($availableFiles as $file) {
            $file = $folderName . DS . $file;
            if (is_file($file)) unlink($file);
        }
        $script = "$(document).ready(function() {\n" . implode("\n", setScript()) . "});";
        file_put_contents($fileName, $script);
        $url = loadClass('Url', 'helpers');
        return "<script type='text/javascript' src='" . $url->baseUrl() . 'public/generated/' . $jsFileName . "'></script>";
    }
}

if (!function_exists('alert')) {
    function alert($message, $returnScript = false)
    {
        if (isAjax()) {
            if ($returnScript) {
                return "\nalert('$message');\n";
            }
            echo "\nalert('$message');\n";
        } else {
            setScript("\nalert('$message');\n");
        }
    }
}

Please suggest if this is a good practice in doing so or any other way i can do it.

Approx 30-40 users would be logged in to the website concurrently and would have approx 5-10 page requests per second. (These are projections. Might go high).

is writing js file (to the hard drive) and linking it is a good practice or just adding the raw scripts to the html body is a good practice since writing to js file gets the js to be un-intrusive.

Also, the javascript generated is going to be dynamic, probably for every page request.

Upvotes: 0

Views: 173

Answers (1)

Michael Coxon
Michael Coxon

Reputation: 5510

If you can see no other choice than dynamically generating every time (my guess is that the content of the script is at least 80% different for each request) then write the script directly into the html file as linking will cause the browser to make another request to include the script.

You are already going to have degraded performance by dynamically generating the file.

The best way of doing this that I can think of is to actually create a php script that generates the js by itself and then create a .htaccess rewrite rule to rewrite /script/generator/{HASH_FOR_REQUEST}.js to /path/to/php-script-generator.php so that you can leverage browser caching if the request is the same.

However, if it is only specific details about the JS that change and the js functions body remains pretty similar (ie, you are using the js to report info back to the client) then consider writing the js in a php file and then using php inline tags to echo the stuff you need to change.

For example:

This script will write an alert to the js so then when loaded with a query string it will report back what is in the query...

<?php
    // disable output buffering 

    /* the reason for this is that the browser will wait 
     * for the first byte returned before continuing with the page. 
     * If it has to wait for the whole file performance will be degarded.
     */

    while(ob_get_level() != 0) ob_end_clean();    

    header("Content-type:text/javascript");

    // it is wise to set some cache headers here


    if(isset($_GET['message']) {
        $message = urldecode($_GET['message']);
    } else {
        $message = "No message!";
    }
?>

// write the js...
alert("<?php echo $message; ?>");

By requesting /path/to/script.php?message=hello+world the script will return alert("hello world");

Upvotes: 2

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