懒加载disqus

disqus.lazyload.js

(function () {
        var disqus_shortname = 'evanyoublog',
            el = document.getElementById('disqus_thread')

        window.addEventListener('scroll', checkPosition)
        window.addEventListener('load', checkPosition)

        function checkPosition () {
            var rect = el.getBoundingClientRect()
            if (rect.top < window.innerHeight) {
                window.removeEventListener('scroll', checkPosition)
                window.removeEventListener('load', checkPosition)
                loadDisqus()
            }
        }

        function loadDisqus () {
            var dsq = document.createElement('script'); dsq.type = 'text/javascript'; dsq.async = true;
            dsq.src = '//' + disqus_shortname + '.disqus.com/embed.js';
            (document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(dsq);
        }
    })()