This MODX snippet retrieves CSS and JS files from your local file system, which is handy when you are adding a revision suffix to your build files.

getAsset.snippet.php

<?php
/**
 * getAsset
 * v.0.0.2
 * 
 * This snippet retrieves CSS and JS files from your local file system,
 * which is handy when you are adding a revision suffix to your build files.
 * For example: 's.min.cdbbec54.js' or 'c.min.543e2b40.css'.
 * 
 * The script attempts to serve and look for the latest file in 
 * the specifed file path in the following format (any other pattern 
 * will be filtered out):
 * 
 * - c.min.<8 character hash>.css
 * - ie.min.<8 character hash>.css
 * - s.min.<8 character hash>.js
 * 
 * Example usage:
 * 
 * [[getAsset? &cssPath=`/assets/css` &jsPath=`/assets/js`]]
 * [[+getasset.js]]
 * [[+getasset.css]]
 * [[+getasset.css_ie]]
 * 
 * Call the snippet cached!
 */
 
// get css asset path from snippet parameter
$cssPath = $cssPath ?: '/assets/template/c';
// get js asset path from snippet parameter
$jsPath = $jsPath ?: '/assets/template/j';

// accept file beginning with 's'
// followed by .min.
// followed by any 8 digit hash
// ending in js
$pattern_js = '/^(s).min.*\S{8}.js$/';

// accept files beginning with 'c' or 'ie'
// followed by .min.
// followed by any 8 digit hash
// ending in css
$pattern_css = '/^(c).min.*\S{8}.css$/';
$pattern_css_ie = '/^(ie).min.*\S{8}.css$/';

// define what folder to look in and apply the pattern match
$asset_array_js = preg_grep($pattern_js, scandir('.' . $jsPath));
$asset_array_css = preg_grep($pattern_css, scandir('.' . $cssPath));
$asset_array_css_ie = preg_grep($pattern_css_ie, scandir('.' . $cssPath));

$asset_array_js_sortby = array();
$asset_array_css_sortby = array();
$asset_array_css_ie_sortby = array();

// for each js asset in the folder...
foreach ($asset_array_js as $value) {
    // get timestamp
    $last_modified = filemtime( '.' . $jsPath . '/' . $value);
    // add timestamp to new array
    $asset_array_js_sortby[] = array(
        'asset' => $value,
        'timestamp' => $last_modified
    );
}

// for each css asset in the folder...
foreach ($asset_array_css as $value) {
    // get timestamp
    $last_modified = filemtime( '.' . $cssPath . '/' . $value);
    // add timestamp to new array
    $asset_array_css_sortby[] = array(
        'asset' => $value,
        'timestamp' => $last_modified
    );
}

// for each css ie asset in the folder...
foreach ($asset_array_css_ie as $value) {
    // get timestamp
    $last_modified = filemtime( '.' . $cssPath . '/' . $value);
    // add timestamp to new array
    $asset_array_css_ie_sortby[] = array(
        'asset' => $value,
        'timestamp' => $last_modified
    );
}

// sort arrays based on timestamp, to ensure we get the latest asset
usort($asset_array_js_sortby, function ($a, $b) { 
    return $b["timestamp"] - $a["timestamp"]; 
});

usort($asset_array_css_sortby, function ($a, $b) { 
    return $b["timestamp"] - $a["timestamp"]; 
});

usort($asset_array_css_ie_sortby, function ($a, $b) { 
    return $b["timestamp"] - $a["timestamp"]; 
});

// take the first result in the array 
$latest_css = reset($asset_array_css_sortby);
$latest_ie = reset($asset_array_css_ie_sortby);
$latest_js = reset($asset_array_js_sortby);

// take value from asset key (the filename);
$css = $latest_css['asset'];
$ie = $latest_ie['asset'];
$js = $latest_js['asset'];

// set placeholders and apply namespace
$output = $modx->setPlaceholders(array (
    'css' => $css,
    'css_ie' => $ie,
    'js' => $js
), 'getasset.');
    
return $output;