resource-path.js

import {normalize} from 'path';

export default ResourcePath;

function ResourcePath (value) {
	this.value = normalize(value);
}

ResourcePath.prototype.add = function () {
	var result = this.value;
	for (var i = -1, l = arguments.length; ++i < l;) {
		result += '/' + arguments[i];
	}

	return new ResourcePath(result);
};

ResourcePath.prototype.toString = function () {
	return this.value;
};

usage.js

import ResourcePath from 'resource-path.js';

var api = new ResourcePath('https://api.github.com');
// .value => https://api.github.com

var wryk = api.add('users', 'wryk');
// .value => https://api.github.com/users/wryk

var issues = wryk.add('issues');
// .value => https://api.github.com/users/wryk/issues

wryk.value === wryk.toString();
// => true