Re-Query Select All the Things!

var qs = parent => (query,all) => (typeof(parent) === "string") ? qs(qs()(parent))(query,all) : (parent||document)[`querySelector${(all||false)?"All":""}`](query);

var qs = parent => query => {let q; return (typeof(parent) === "string") ? qs(qs()(parent))(query) : (q = (parent||document).querySelectAll(query)).length > 1 ? q : (q[0]||null);};

// Let's review (assuming strict mode is not initially set in this figure)
five = 5; // => 5 (because the assignment operator returns the value that is assigned to the variable; because strict mode is not enabled, five is hoisted, and can be initialized without declaration first)
var six; // => undefined (declaration keywords (var, let, and const) return undefined even though the variable. If six was previously used, it would have been hoisted.)
var seven = 7; // => undefined (although 7 is assigned to seven; seven is declared and assigned so technically it's hoisted)
var num = x => {
 "use strict";
 let w;  // => undefined (although w is defined)
 y = x;  // => ReferenceError (because y was not defined)
 w = (var z=[x,y,3]).length; // SyntaxError (because unexpected token "var" next to z) (also, if it had worked the code inside the parenthesis would have returned undefined, of which undefined.length is a TypeError)
 return w;
};

//Remember that this form, known as FUNCTIONAL FORM,...
var f = x => x;
// Means the same as this form, known as FUNCTIONAL-IMPERATIVE FORM,...
var f = x => { return x; }
// Means the same as this form known as IMPERATIVE FORM
var f = function(x){ return x; }

/* @func: qs
 * @desc: querySelector[All] in one function
 * @param parent : (@default is document) A string or Element to find the query element(s)
 * @param query  : (required) A CSS string matching an id, class, or attribute of elements inside the parent.
 * @returns:
 *  null if nothing is found.
 *  Node if query matches one result.
 *  NodeList query matches more than one result.
 */
var qs = function(parent){
  return function(query){
    let q;	// q is declared in the inner function
    if(typeof(parent) === "string"){
      let parent_query = qs()(parent);
      return qs(parent_query)(query);
    } else {
      // If parent is undefined, use document.
      var parent_element = parent || document;
      q = parent_element.querySelectorAll(query);
      if(q.length > 1){
        // if q match more than one instance return all matches as a NodeList.
        return q;	  
      } else {
        // Otherwise, return the first element only
        // Note: If [] is returned, and [][0] is undefined (meaning no matches), return null.
        return (q[0]||null);
      }
    }
  } // inner function
} // outer function