bem-linter-dumb.js

(function bemLinter(){
    const namespaces = ['o', 'c', 'u', 's', 't', 'is', 'has'];
    const suffixes = ['xs', 's', 'ms', 'sm', 'md', 'lg', 'l', 'xl', 'print'];

    const SEVERITY_ERROR = 'error';
    const SEVERITY_WARNING = 'warn';
    const SEVERITY_INFO = 'info';

    const ERR_TYPE_STRAY_ELEMENT = 'stray-element';
    const ERR_TYPE_MISSING_NAMESPACE = 'missing-namespace';
    const ERR_TYPE_INVALID_SUFFIX = 'invalid-suffix';
    const ERR_TYPE_CAMELCASE = 'camelcase';
    const ERR_TYPE_MISSING_NON_MODIFIED = 'missing-non-modified';

    /** cls has to have a namespace [deactivated - only for itcss] */
    const namespaceChecker = (node, cls) => {
        const regex = new RegExp(`^_?(${namespaces.join('|')})-.`);
        return {
            success: regex.test(cls),
            message: `${cls} needs to start with a namespace. possible namespaces are: ${namespaces.join(', ')}`,
            severity: SEVERITY_ERROR,
            type: ERR_TYPE_MISSING_NAMESPACE
        };
    };

    /** cls either needs no suffix, or a valid one */
    const mediaSuffixChecker = (node, cls) => {
        const regex = /@(.*?)$/;
        const match = cls.match(regex);

        if(!match){
            return { success: true };
        }

        return {
            success: suffixes.indexOf(match[1]) !== -1,
            message: `${cls} has an invalid suffix of '${match[1]}'. possible suffixes are: ${suffixes.join(', ')}`,
            severity: SEVERITY_ERROR,
            type: ERR_TYPE_INVALID_SUFFIX
        }
    };

    /** cls has to be all lowercase */
    const camelcaseChecker = (node, cls) => {
        return {
            success: cls.toLowerCase() === cls,
            message: `${cls} needs to be all-lowercase. no camleCase allowed`,
            severity: SEVERITY_ERROR,
            type: ERR_TYPE_CAMELCASE
        }
    };

    /** modifiers can't stand alone */
    const nonModifiedChecker = (node, cls) => {
        const regex = /^(.*?)--/;
        const match = cls.match(regex);

        if(!match){
            return { success: true };
        }

        return {
            success: node.classList.contains(match[1]),
            message: `the modifier ${cls} doesn't have a matching block or element on the same element ${match[1]}`,
            severity: SEVERITY_ERROR,
            type: ERR_TYPE_MISSING_NON_MODIFIED
        };
    };

    /** element has to be inside a block */
    const strayElementChecker = (node, cls) => {
        const regex = /^(.*?)__/;
        const match = cls.match(regex);

        if(!match){
            return { success: true };
        }

        while(node.parentElement){
            node = node.parentElement;
            if(node.classList.contains(match[1])){
                return { success: true };
            }
        }

        return {
            success: false,
            message: `the element ${cls} is not contained within the parent-block ${match[1]}`,
            severity: SEVERITY_ERROR,
            type: ERR_TYPE_STRAY_ELEMENT
        };
    };


    /** prints messages as collapsed console-entries */
    const printMessages = messages => {
        let lastType = null;

        messages
            .sort((a, b) => a.type < b.type ? -1 : a.type > b.type ? 1 : 0)
            .forEach(msg => {
                if(msg.type !== lastType){
                    console.groupEnd();
                    console.groupCollapsed(msg.type);
                    lastType = msg.type;
                }
                console[msg.severity](msg.message, msg.node);
            });

        console.groupEnd();
    };


    const checkers = [
        // namespaceChecker
        mediaSuffixChecker,
        camelcaseChecker,
        nonModifiedChecker,
        strayElementChecker
    ];

    const messages = [];
    const walker = document.createTreeWalker(document.body, NodeFilter.SHOW_ELEMENT);

    while(walker.nextNode()){
        const node = walker.currentNode;

        if(node.classList.length === 0){
            continue;
        }

        node.classList.forEach(cls => {
            checkers.forEach(checker => {
                const message = checker(node, cls);
                if(message.success){
                    return;
                }

                messages.push({
                    node,
                    message: message.message,
                    severity: message.severity,
                    type: message.type
                });
            });
        });
    }

    printMessages(messages);
})();