code: function assignVal(obj, prop, userVal, defaultVal) {
    const val = userVal !== undefined ? userVal : defaultVal;
    if (val !== undefined) {
      obj[prop] = val;
    }
  }
docs: /*
  Helper to create properties and assign values in an object.
  Properties with `undefined` values are ignored. *mutative*
  
  @param {object} obj Object to assign properties to