proxy 利用get拦截，实现一个生成各种DOM节点的通用函数dom。

    const dom = new Proxy({}, {
        get(target, property) {
            return function(attrs = {}, ...children) {
                const el = document.createElement(property);
                for (let prop of Object.keys(attrs)) {
                    el.setAttribute(prop, attrs[prop]);
                }
                for (let child of children) {
                    if (typeof child === 'string') {
                        child = document.createTextNode(child);
                    }
                    el.appendChild(child);
                }
                return el;
            }
        }
    });

    const el = dom.div({},
            'Hello, my name is ',
            dom.a({href: '//example.com'}, 'Mark'),
            '. I like:',
            dom.ul({},
                    dom.li({}, 'The web'),
                    dom.li({}, 'Food'),
                    dom.li({}, '…actually that\'s it')
            )
    );

    document.body.appendChild(el);