// 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.querySelector("#test-div").querySelectorAll(".c-red.c-green p");

// 选择<p>Haskell</p>: var haskell = document.querySelector("#test-div div:last-child p:last-child");