Memoization in JS - Fibonacci example

fibonacci.js

var Utils = {
  memo: {},
  fibonacci: function (n) {
    var that = this, val;
    if (n in that.memo) {
      return that.memo[n];
    }
    else {
      if(n === 0 || n === 1) {
        val = n;
      } 
      else {
        val = that.fibonacci(n - 1) + that.fibonnacci(n - 2);
      }
      
      that.memo[n] = val;
      return val;
      
    }
  }
}