gistfile1.js

function $(selector, context)
{
    if (!(context instanceof Element)) {
      context = document;
    }
    
    return context.querySelectorAll(selector);
}

// querySelectorAll() returns a NodeList object so we need to get the first one
parent = $('.parent', document.body)[0];

child1 = $('.child-1', parent)[0]; // parent is the context element (fast search)

child2 = $('.child-2')[0]; // will search in the entire document