posthtml recursive tree walker to add first-child/last-child classes to all elements

posthtml-walker-first-last-child.js

var iteration = 0,
    maxIterations = 200;

function addClass(node, className) {
    var classNameRegex = new RegExp(className, "g");

    node.attrs = node.attrs || {};

    if(!node.attrs.class || !classNameRegex.test(node.attrs.class)) {
        node.attrs.class = node.attrs.class ? node.attrs.class + " " + className : className;
    }
}

function removeClass(node, className) {
    var classNameRegex = new RegExp(className, "g");

    node.attrs = node.attrs || {};

    if(node.attrs.class || classNameRegex.test(node.attrs.class)) {
        node.attrs.class = node.attrs.class.replace(classNameRegex, "");
    }
}

function walker(node) {
    var firstNode = false,
        prevNode = false;

    ++iteration;

    if(iteration > maxIterations) {
        console.log("ERR! exceeded max iterations");

        return node;
    }

    if(!node.tag || !node.content.length) {
        return node;
    }

    node.content.forEach((child) => {
        if(child.tag) {
            if(!firstNode) {
                firstNode = true;
                child.attrs = child.attrs || {};

                addClass(child, "first-child");
            }

            if(prevNode) {
                removeClass(prevNode, "last-child");
            }

            addClass(child, "last-child");
            prevNode = child;
        }

        if(child.content) {
            child = walker(child);
        }
    });

    return node;
}