// 选择<p>JavaScript</p>:

var js = document.querySelector('#test-p');

// 选择<p>Python</p>,<p>Ruby</p>,<p>Swift</p>:

var arr = document.querySelectorAll('.c-red.c-green p');

// 选择<p>Haskell</p>:

var haskell = document.querySelector('.c-green.c-red+.c-green p:nth-of-type(2)');