<?php
$file = isset($argv[1]) ? $argv[1] : null;
if (empty($file)) {
    printf("USAGE: %s file.js", $argv[0]);
    exit;
}

if (!is_file($file)) {
    printf("ERROR: File does not exist: %s", $file);
}

$content = file_get_contents($file);

$content = preg_replace_callback('/`(.*?)`/s', function($groups) {
    $value = $groups[1];

    $value = preg_replace_callback("/(\r?\n)/", function($groups) {
        return '\n\\' . $groups[1];
    }, $value);

    $quote = '"';
    $value = $quote. addcslashes($value, $quote) . $quote;

    return $value;
}, $content);

file_put_contents($file, $content);