The tic-tac-toe project presented itself with a problem of "checking for a win state", this gist contains an elegant non-performant, and a less-elegant performant solution.

tic-tac-toe elegant vs performant solutions

/* 
Background:  
  - The Grid object has an array of Vector objects accessible in the Grid's "vectors" attribute
  - A Vector object has a "value" attribute that contains "O", "X", or null if not set
  - The checkForWin method on the Grid returns true if and only if there is a win state in tic-tac-toe
    * The win state is determined by looping through all the various winCombos, where winCombos is an array of arrays, whose inner arrays represent the 3 indexes of the Grid's "vectors" array that refer to row, collumn, or diagonal on a tic-tac-toe board which -if all containing the same Vector "value" value- constitutes a win.
*/


// Elegant, non-performant
Grid.prototype.checkForWin = function() {
  //var surroundingVectors = this.getSurroundingVectors(index);

  var winCombos = [[0,1,2], [3,4,5], [6,7,8], [0,3,6], [1,4,7], [2,5,8], [0,4,8], [2,4,6]];
    
  var self = this;
    
  //The current win combo reduce needs to be refactored into it's own function
  return winCombos.reduce(function(previousValue, currentWinCombo) {
    return previousValue || currentWinCombo.reduce(function(w,el,i,arr){
      return w && (arr.length-1 == i || (self.vectors[el].value != null && self.vectors[el].value == self.vectors[arr[i+1]].value))
    }, true)
  }, false)
}

// Less elegant, performant
Grid.prototype.checkForWin = function() {
    //var surroundingVectors = this.getSurroundingVectors(index);

    var winCombos = [[0,1,2], [3,4,5], [6,7,8], [0,3,6], [1,4,7], [2,5,8], [0,4,8], [2,4,6]];

    var self = this;

    //The current win combo reduce needs to be refactored into it's own function
    return winCombos.some(
      function(currentWinCombo) {
        if (currentWinCombo.every(
          function(el, i, cwc) {
            console.log("in currentWinCombo.every, el: " + el + ", i: " + i + ", cwc: " + cwc);
            if (cwc.length-1 == i) {
              console.log("COMPLETE MATCH FOUND ON CURRENTWINCOMBO!");
              return true;
            }
            else if (self.vectors[el].value == null || self.vectors[el].value != self.vectors[cwc[i+1]].value) {
              console.log("NO MATCH ON CURRENTWINCOMBO! BREAKING");
              return false;
            }
            else {
              console.log("MATCHED SO FAR ON CURRENTWINCOMBO! KEEP GOING!");
              return true;
            }
          })) {
          console.log("FOUND A WIN!!! BREAKING!");
          return true;
        }
        else {
          console.log("NO WIN FOUND!!! KEEP GOING!");
          return false;
        }
      })
}