Function getLanguageForBlock

src/util.js:17–44

(block)

 * @return {string|null}
 */
export function getLanguageForBlock(block) {

    // If this doesn't have a language but the parent does then use that.
    //
    // This means if for example you have: <pre data-language="php">
    // with a bunch of <code> blocks inside then you do not have
    // to specify the language for each block.
    let language = block.getAttribute('data-language') || block.parentNode.getAttribute('data-language');

    // This adds support for specifying language via a CSS class.
    //
    // You can use the Google Code Prettify style: <pre class="lang-php">
    // or the HTML5 style: <pre><code class="language-php">
    if (!language) {
        const pattern = /\blang(?:uage)?-(\w+)/;
        const match = block.className.match(pattern) || block.parentNode.className.match(pattern);

        if (match) {
            language = match[1];
        }
    }

    if (language) {
        return language.toLowerCase();
    }

    return null;
}

/**
 * Determines if two different matches have complete overlap with each other