Simple path join and dirname functions for generic javascript

path.js

'uses strict';

// Joins path segments.  Preserves initial "/" and resolves ".." and "."
// Does not support using ".." to go above/outside the root.
// This means that join("foo", "../../bar") will not resolve to "../bar"
const join = function(/* path segments */) {
    // Split the inputs into a list of path commands.
    var parts = [];
    for (var i = 0, l = arguments.length; i < l; i++) {
        parts = parts.concat(arguments[i].split('/'));
    }
    // Interpret the path commands to get the new resolved path.
    var newParts = [];
    for (i = 0, l = parts.length; i < l; i++) {
        var part = parts[i];
        // Remove leading and trailing slashes
        // Also remove "." segments
        if (!part || part === '.') continue;
        // Interpret ".." to pop the last segment
        if (part === '..') newParts.pop();
        // Push new path segments.
        else newParts.push(part);
    }
    // Preserve the initial slash if there was one.
    if (parts[0] === '') newParts.unshift('');
    // Turn back into a single string path.
    return newParts.join('/') || (newParts.length ? '/' : '.');
};
  
// A simple function to get the dirname of a path
// Trailing slashes are ignored. Leading slash is preserved.
const dirname = function(path) {
    return join(path, '..');
};

module.exports.join = join;
module.exports.path = dirname;